c(1000)=400(1000)-.2[tex] (1000)^{2} [/tex]
c(1000)=400,000-200,000=200,000
c(2000)=400(2000)-.2[tex] (2000)^{2} [/tex]
c(2000)=800,000-800,000=0
So, 1000 units is going to cost $200,000. I'm not sure how that works with minimum and maximum since it is an exact answer.
Hope that helps though.