1. C(x)=2200 + 5x + 0.002x^2 + 0.00013x^3 (a) Find the average cost function and sketch it (b.) At what production level is the average cost minimized? 2. Relevant equations My book defines the average cost as c(x)=C(x)/x And the average cost is minimized when C'(x) = c(x) 3. The attempt at a solution I'm supposed to be teaching the class this and the teacher gave me the answers for this problem but I don't know how he got them. He has the final answer of (a) at c(x) = 2200/x + 0.002x + 0.00013x^2 But I have it at c(x) = (2200 + 5x + 0.0002x^2 + 0.00013x^3)/x I thought that he might have taken the derivative however the numbers aren't right in his answer for that to have happened.