(60,58200) , (90,85200)
slope = (85200 - 58200) / (90 - 60) = 27,000/30 = 900
y = mx + b
slope(m) = 900
(60,58200)...x = 60 and y = 58200
sub and find b, the y int
58200 = 900(60) + b
58200 = 54000 + b
58200 - 54000 = b
4200 = b
ur equation is : C(x) = 900x + 4200 <== ur equation