Question 107556
The equation is linear, so it will have the form {{{C = ax + b}}}
Cis plotted on the vertical axis, because it is the 
"dependant" variable (dependant on x items produced)
x is the independant variable plotted on the horizontal axis.
b is the "C intercept". It's the cost of producing zero items
(overhead). From the points P2(x2,C2) and P1(x1,C1) 
 I can determine the slope, a
{{{a = (C[2] - C[1]) / (x[2] - x[1])}}}
where
{{{C[2] = 22000}}}
{{{C[1] = 10000}}}
{{{x[2] = 300}}}
{{{x[1] = 100}}}
{{{a = (22000 - 10000) / (300 - 100)}}}
{{{a = 12000 / 200}}}
{{{a = 60}}}
Now I have {{{C = 60x + b}}}
I'll pick one of the points P(x,C) to solve for b
{{{10000 = 60*100 + b}}}
{{{b = 10000 - 6000}}}
{{{b = 4000}}}
{{{C = 60x + 4000}}} answer