You want to separate all the coal particles having a diameter of $100 \mu \mathrm{m}$ or larger from a slurry. To do this, the slurry is pumped into the bottom of a large tank. It flows upward and overflows over the top of the tank, where it is collected in a trough. If the coal has $S G=1.4$ and the total flow rate is $250 \mathrm{gpm}$, how big should the tank be?