Question 1. A vessel contains gasoline that flows out from a small hole at point O in the base of the vessel. At time $t$, in minutes, the height of the gasoline surface above O is $y$, and the rate at which $y$ is decreasing is inversely proportional to $y^{3/2}$. Write down the differential equation which expresses $\frac{dy}{dt}$ in terms of $y$. Given that $y = 25$ when $t = 0$ and that $y = 16$ when $t = 30$, find the value of $t$ when $y = 0$.
