2' (20 marks) Suppose the value of timber (already planted on some given land) is the following mction of time: V(t) =10000+6000t10t2 in dollars. Assuming the continuously discount rate (lending and borrowing rate) is 5% and assuming zero upkeep cost during the period of timber growth, (a) what is the optimal time to cut the timber for sale? (b) What is the maximum present value of timber? (dV/dt=6000-20t)