The price p, in dollars, of a certain product
and the quantity x sold obey the demand equation

p= -1/4x + 100 0≤x≤ 400

Suppose that the cost C, in dollars, of producing x units is

C = x^1/2/ 25 +600
(the square root of x over 25)

Assuming that all items produced are sold, find the cost C as a function of the price p.
[Hint: Solve for x in the demand equation and then form the composite function.]