If p(x) is the total value of the production when there are x workers in a plant,

Question:

If p(x) is the total value of the production when there are x workers in a plant, then the average productivity of the workforce at the plant is
A(x) = p(x) /x
(a) Find A'(x). Why does the company want to hire more workers if A'(x) > 0?
(b) Show that A'(x) > 0 if p'(x) is greater than the average productivity.