If $f(x) = -6\pi ^{6}$ then $\frac{df}{dx} =$
The slope of the tangent line to $f$ at $x = -6$ is
If $v(t) = -6\pi ^{6}$ is the velocity of a motorcycle (in miles per hour) at time t (in hours), find the acceleration of the car at time $t = 9$ with units: