1. The problem statement, all variables and given/known data The cost of producing x units is given by: f(x)=800+110x-110ln(x) Find the minimum average cost. x >= 1 2. Relevant equations Cost=f(x)/x Marginal cost is C'(x) 3. The attempt at a solution This is what I have done so far: C(x)=(800+110x-110ln(x))/x C'(x)= (110ln(x)-910)/x^2 setting C'(x)=0 I get x=e^(910/110) C''(x)=(1930-220ln(x))/x^3 Plugging in my value for x I get an increasing number validating, or I thought my x=value. Webwork tells me that e^(910/110) is incorrect for the minimum cost.