Bunuel
Sue's monthly earnings consist of a monthly salary and a 4 percent commission on the portion of her monthly sales that is in excess of $2,000. If Sue's monthly salary was the same in July as in August, how much greater were her sales in July than in August?
(1) Sue's monthly earnings were $3,620 in July and $3,580 in August.
(2) Sue's monthly salary was $3,500 in July and in August.
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KarishmaB BunuelI cannot wrap my head around how option A is the correct answer. The question stem neither mentions that Sue received a commission in both months nor provides any information on Sue's monthly salary. Hence, I would consider Statement 1 not sufficient.
For example, let's consider the following two cases for
Statement 1Case 1- Month : July
Monthly Salary: $3580
Sale: $3000
Monthly Earnings = $3580 + 0.04(3000-2000) = 3580 + 40 = $3620
- Month : August
Monthly Salary: $3580
Sale: $1000
Monthly Earnings = $3580
Difference in sale = 3000 - 1000 = $2000
Case 2- Month : July
Monthly Salary: $3500
Sale: $5000
Monthly Earnings = $3500 + 0.04(5000-2000) = 3500 + 120 = $3620
- Month : August
Monthly Salary: $3500
Sale: $4000
Monthly Earnings = $3500 + 0.04(4000 - 2000) = 3500 + 80 = $3580
Difference in sale = 5000 - 4000 = 1000
Isn't Statement 1 giving us two possible answers or how did we conclude that the sales made by Sue were greater than $2000 in both months, thereby making her eligible for commissions on both months?
What am I missing here

Could you please help me?
Edit: I believe that the answer posted in GMAT Prep is not correct.
IMO The correct answer to this question should be Option C