Suppose that $f(x) = -5 x^2 - 5 x$.

(A) Find $f'(x)$.

$f'(x)$ =

Find the slope of the tangent lines to the graph of $f$ at each of the following values of $x$:

(B) Slope at $x = 3$:

(C) Slope at $x = 6$:

(D) Slope at $x = 8$: