Answer
A
Explanation:
First, lets go through B-D and explain why they are correct.
B= f represents the number of flash drives. This means that the coefficient, 10, would be the cost per flash drive.
C= n represents the number of cases of paper. it says so in the question, so that one is a bit easier.
D= f represents the amount of packages of hanging folders. If the coefficient for B is the cost, then that would be the same case for D. Therefore it is correct because the coefficient is 13.
A would be incorrect because the coefficient represents the amount that one item costs. P is the packs of pencils, meaning that it would be $7 per pack of pencils.
Hope this helps!