Question 442071
Treat this as a linear equation with two points.
y=mx+b
x =3 y=500
(3,500)
x=4 y=300
(4,300)
So we have two points on the line.
and we want the formula (equation)
 where we use D(p) for y and p for x
D(p)=mp+b
m=change in y over the change in x
(500-300)/3-4
-200 is m
D(p)=-200p+b
500=-200*3+b
500=-600+b
1100=b
D(p)=-200p+1100