The cost function π C(x) = 140 + 15x - 0.8x² π. Find the Marginal average cost function.
a) π C'(x) = 15 - 1.6x π
b) π C'(x) = 15 + 1.6x π
c) π C'(x) = 15 - 0.8x π
d) π C'(x) = 15 + 0.8x π