Suppose x and y are related by the equation -12x + x³ + y + y² = 4

(a) Find all critical points on the curve.
(b) Determine whether the critical points found in part (a) are relative maxima or relative minima by taking values of x nearby and solving for the corresponding values of y.
(c) Is there an absolute maximum or minimum for x and y in the relationship given in part (a)? Why or why not?