A club is buying boxes of candy bars to sell for a fundraiser. If each box contains c candy bars, and each member sells x bars a day, how many boxes are needed to supply enough candy bars for 3c members to sell for 5 days?

A) 15c(^2) x

B) x/15

C) (3x)/5

D) (15c^{2)}/x

E) 15x

I have no concept how to do this. I tried to plug in, by assuming c=200, and x=2. So 200 bars were sold in 100 days by one member. And now i'm at a loss with what to do....Answer is 15x (E)