need max and min points for c(x)=-0.001x+2+2000/x
c ' (x) = -.001 - 2000/x^2
= 0 for max/mins
-.001 = 2000/x^2
x^2 = 2000/.001 = a negative.
that is not possible, so there are no max or min points
Here is a picture of your problem
http://www.wolframalpha.com/input/?i=plot+y+%3D-0.001x%2B2%2B2000%2Fx