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In this question, I am not able to understand that why everyone has assumed the cost of FD as ~0. But the questions mentions that cost of FD is negligible if the CM have already SD. It means that the cost of FD is approx same as SD, but obviously cost of FD is not 0
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Hello experts and GMATNinja
I found the answer A quite confusing given the following scenario:

Current scenario:
------------------------Fast dialing---Slow dialing---Total
Price per customer-------10---------------8
Cost per customer--------5----------------6
profit per customer-------5----------------2
# of customers-----------3----------------7---------- 10
Total profits--------------15---------------14----------29


New scenario: all customers switch to FD at revenue of 8$ per customer
------------------------Fast dialing
Price per customer------8
Cost per customer-------5
profit per customer------3
# of customers----------10
Total profits--------------30

So basically in this scenario, the proposal to switch all customers to FD would increase total profits
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Understanding the argument -
Clearbell Telephone provides slow-dialing (SD) service to customers for a low fee, and fast-dialing (FD) service to other customers who pay a somewhat higher fee. - Fact.
FD technology, however, is so efficient that it costs Clearbell substantially less per average call to provide than does SD. - Fact. Notice that "average" is an adjective here. So basically, the Cost per call for FD is less than the cost per call for SD
Nonetheless, accountants have calculated that Clearbell's profits would drop if it provided FD to all its customers at the current low-fee rate. - Contrast.

Option Elimination -

Let's take quick numbers to understand -

SD
Price - $10 per call.
Cost - $8 per call
No. of calls - 10

FD -
Price - $20 per call.
Cost - $5 per call
No. of calls - 10

Profit = Revenue - Cost = $300 - $130 = $170

In the scenario, what accountants have calculated? Provide FD to all its customers at the current low fee rate.
FD -
Price - $10 per call.
Cost - $5 per call
No. of calls - 20

Profit = Revenue - Cost = $200 - $100 = $100

Profits have dropped from $170 to $100.

A. The extra revenue collected from customers who pay the high fee is higher than the extra cost of providing SD to customers who pay the low fee. - Extra revenue from FD = 20*10 - 10*10 = $100. The extra cost of SD = $80-$50 = $30. So the impact of extra revenue (the dip) is much more than what we save on the cost, thus the dip in the profits from $170 to $100. Ultimately we saved on the cost but the revenues dropped significantly and thus lower profits.

B. The low fee was increased by 6 percent last year, whereas the higher fee was not increased last year. - Out of scope.

C. Although 96 percent of customers regard FD service as reliable and more convenient than SD, fewer than 10 percent of them choose to pay the higher fee for FD service. - It is out of scope as accountants calculate the profits to provide at SD price and cost of FD. Customers' preference, in that case, is out of scope.

D. The company's competitors generally provide business customers with FD service at low-fee rates. - other companies are out of scope.

E. Profits rose slightly each month for the first three months after FD was first offered to customers, then fell slightly each month for the succeeding three months. - Opposite of what accountants predict. Moreover, we don't know the impact of a slight price rise and further a slight fall.
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MinhChau789
Hello experts and GMATNinja

I found the answer A quite confusing given the following scenario:

Current scenario:

------------------------Fast dialing---Slow dialing---Total

Price per customer-------10---------------8

Cost per customer--------5----------------6

profit per customer-------5----------------2

# of customers-----------3----------------7---------- 10

Total profits--------------15---------------14----------29

New scenario: all customers switch to FD at revenue of 8$ per customer

------------------------Fast dialing

Price per customer------8

Cost per customer-------5

profit per customer------3

# of customers----------10

Total profits--------------30

So basically in this scenario, the proposal to switch all customers to FD would increase total profits
­Your "current scenario" seems to go against one of the conditions mentioned in the passage: "FD technology costs substantially less per average call to provide than does SD". In your model, they appear to cost about the same (5 and 6, respectively).

Regardless, remember that we're looking for the answer choice that, if true, BEST explains the results of the accountants' calculation. We're not looking for something that PROVES that profits will go down, so there's no point in hunting for the edge case where (A) is true and profits go up.

Let's keep it simple:
  • (A) basically says that the extra fees for FD outweigh the extra cost of providing SD.
  • So maybe you earn an extra $1,000,000/month in fees for FD and pay an extra $200,000/month for the people still on SD.
  • If you switch everyone to SD pricing, you'll save $200,000 but lose the extra $1,000,000 in fees.

That would certainly explain the results of the accountants' calculations, so (A) works.

I hope that helps!­­
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Mathematically lets visualize why Option A is correct:

As per given question stem:

R_FD > R_SD & C_FD < C_SD [Eq. 1 & 2]

Current profit (CP): (R_FD + R_SD) - (C_FD + C_SD) [Eq. 3]

As per Option A:

R_FD - R_SD > C_SD - C_FD (Extra revenue > Extra cost) [Eq. 4]

Now new profit according to scheme mentioned: (NP) = (R_SD + R_SD) - (C_FD + C_FD) -> 2(R_SD - C_FD) [Eq. 5]

Check whether profit reduces or not: CP - NP -> (R_FD + R_SD) - (C_FD + C_SD) - 2(R_SD - C_FD) -> R_FD - R_SD - (C_SD - C_FD) [Eq.6]

Now from [Eq. 4], we get [Eq. 6] is always positive -> CP - NP is positive, which means current profit is larger than new profit.

Hence profit reduces if new scheme is implemented.

gmatt1476
Clearbell Telephone provides slow-dialing (SD) service to customers for a low fee, and fast-dialing (FD) service to other customers who pay a somewhat higher fee. FD technology, however, is so efficient that it costs Clearbell substantially less per average call to provide than does SD. Nonetheless, accountants have calculated that Clearbell's profits would drop if it provided FD to all its customers at the current low-fee rate.

Assume that installation costs for FD are insignificant if the customer already has SD service. Which of the following, if true about Clearbell, best explains the results of the accountants' calculation?

A. The extra revenue collected from customers who pay the high fee is higher than the extra cost of providing SD to customers who pay the low fee.

B. The low fee was increased by 6 percent last year, whereas the higher fee was not increased last year.

C. Although 96 percent of customers regard FD service as reliable and more convenient than SD, fewer than 10 percent of them choose to pay the higher fee for FD service.

D. The company's competitors generally provide business customers with FD service at low-fee rates.

E. Profits rose slightly each month for the first three months after FD was first offered to customers, then fell slightly each month for the succeeding three months.


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