take the derivative of C w/r to time, set C'(t) = 0 and solve for critical value(s) of t, then use the 1st derivative test to check which critical value(s) yields a minimum.
take the derivative of C w/r to time, set C'(t) = 0 and solve for critical value(s) of t, then use the 1st derivative test to check which critical value(s) yields a minimum.
take the derivative of C w/r to time, set C'(t) = 0 and solve for critical value(s) of t, then use the 1st derivative test to check which critical value(s) yields a minimum.
take the derivative of C w/r to time, set C'(t) = 0 and solve for critical value(s) of t, then use the 1st derivative test to check which critical value(s) yields a minimum.
t = 1 is the critical value in this case and you are checking if there is a maximum. But the idea is the same.