Solve this following
Question:

Oil is leaking at the rate of $15 \mathrm{~mL} / \mathrm{s}$ from a vertically kept cylindrical drum containing oil. If the radius of the drum is $7 \mathrm{~cm}$ and its height is $60 \mathrm{~cm}$, find the rate at which the level of the oil is changing when the oil level is $18 \mathrm{~cm}$.

Solution: