Okay so I stumbled upon this question and I think I may be on the right track but request backup.. :)

A store handles a specialty item that has a marginal cost of $24 and a fixed cost of $360. The sales required to break even are 75 items.

A) Find the linear cost function

My answer was --> c(x) = 24+360

B) Find the linear revenue function

My answer was --> R(x) = px -->R(x) = 384x

Does this look correct?