@DSE 2008 Q39

[subhraminion]

  I tried the way it was mentioned in previous posts but its not coming. Moreover, i tried this one as well
profit=10k+20f-k^2{(5-E)^2-1}-F^2E^2-tE. Anyone?

[sun]

Take t=marginal savings= marginal damage that is t= 10k^2-2k^2 and t= 2EF^2 ( marginal damage)