Given data:
The first point on the graph is (0,20,000).
The second point on the graph is (40,0).
The equattion of the line is,
(y-20,000)/(x-0)=(0-20,000)/(40-0)
(y-20,000)/(x)=-500
y-20,000=-500x
y=-500x+20,000
Thus, the equation of the line is y=-500x+20,000
