The cost of m pencils is the same as the cost of n pens.

Assume m = 5 and n = 4

Let x be the cost of a pen.

Given data: Cost of a pencil - 20 cents

20m = nx

20*5 = 4*x => x = 5*5 = 25 cents

Therefore, if each pencil costs 20 cents, the pens cost 25 cents.

We have been asked to find the cost of 10 pens in dollars,

the cost of 10 pens will be 250 cents or 2.5$

Putting the values of m and n in the answer options, we will be able to arrive at the solution

A. \(\frac{200n}{m} = \frac{200*4}{5} = 250\)$(wrong)

B. \(\frac{2n}{100m} = \frac{2 * 5}{100 * 4} = \frac{1}{40} = 0.25\)$(wrong)

C. \(\frac{2m}{n} = \frac{2*5}{4} = 2*1.25 = 2.5\)$(correct)

Hence,

Option C is the correct answer option.

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