Answer: The below graph representing the volume of water in the pool over time from when the hose is placed in the pool until the pool is full.
Explanation:
It is given that the capacity of pool is 21,000 gallon.
At initial stage the pool contains 9000 gallons.
The capacity of empty pool is,

The water is being added at the rate of 1500 gallons per hour.
So the pool will completely full after,

The two points are (0,9000) and (8,21000).
Plot these two points on a coordinate plane and joint them by a straight line.
And the volume is represented by the equation,

Since 9000 is initial value and rate of range is 1500.