Use the slope formula to find our slope which is m
(y2-y1)/(x2-x1)
So (28,040-14,040)/(400-50)
Gives you (14,000/(350) = 40
40 =slope
Substitution to find b
14,040= 40(50) + b
14,040= 2000 + b
Subtract 2000 from both sides
12,040= b
Now you can find the cost given any number of computers!
Y= 40x + 12,040
I hope this helped!