Answer the following about the function f(x) = 4x3x4500. Justify all your answers. (a) Find all critical numbers of f(x) (2 pts) (b) Where is the function y = f(x) increasing? Justify your answer without graphing the function. (2 pts) (c) Where is the function y = f(x) concave down? Justify your answer without graphing the function. (2 pts)