Average Cost. A cost function is given by C (x) = 5x2 + 2 a. Find the marginal cost function. b. Find the derivative of the average cost function. Hint: The average cost function is _C(x) C(x) = - x c. Find the marginal cost for x = 10. Write a sentence interpreting your result. d. Graph MC(x), C(x), and C'(x) for x between 0 and 4 and the vertical axis between x = -20 and x = 50. Make sure to label all of the functions. e. Make some observations about the relationships between the graphs. Pay close attention to where the graphs intersect