To begin solving this question, I'm going to find the total volume of the pool. Since it is a rectangular prism we get the volume by multiplying the length by the width by the depth.
Now, we know the pool starts with 4500ft³ water. Then it starts to lose 250ft³ each hour. If we divide the total volume by the rate, we're going to find the amount of time needed to empty the pool.
It is going to take 18 hours!