If f(x) is differentiable for the closed interval [-4, 0] such that f(-4) = 5 and f(0) = 9, then there exists a value c, -4 < c < 0 such that:
a. f(c) = 0
b. f '(c) = 0
c. f (c) = 1
d. f '(c) = 1