A)
Number of Gallons drained per hour; Number of hours (Independent Variables)
Number of Gallons in the pool (Dependent Variable)
B) -25 (It's the negative value of how many gallons are drained in an hour)
C)13000 (It means how many gallons were in the pool to begin with)
D)3000 (It's the corresponding value for 40 as the x-value)