A horizontal cylindrical tank has cross-sectional area $A(x)=4\left(6 x-x^{2}\right) m^{2}$ at height $x$ meters above the bottom when $x \leq 3$ .
a. The volume $V$ between heights $a$ and $b$ is $\int_{a}^{b} A(x) d x$ . Find the volume at heights between 2 m and 3 $\mathrm{m}$ .
b. Suppose that oil is being pumped into the tank $\frac{d x}{d t}=\frac{d x}{d V} \frac{d V}{d t},$ at how many meters per minute is the height of oil in the tank changing, expressed in terms of $x,$ when the height is at $x$ meters?
c. How long does it take to fill the tank to 3 $\mathrm{m}$ starting from a fill level of 2 $\mathrm{m} ?$