I need help with C.

1. Consider the function f (x) = x4+ 4x3 - 8x2 + 52 (a) Find the critical numbers of the function. (b) Make a sign diagram for the derivative of the function. Show how you are obtaining the sign of the derivative-don't just guess! (c) Find all open intervals of increase and decrease. (d) Sketch the graph of the function and label any relative maxima or minima