Suppose nowthat the Christmas trees do not have to be sold after 10 years, but could be sold in any year. Their value if they are cut before they are 10 years old is zero. After the trees are 10 years old, an acre of trees is worth $1,000 and its value will increase $100 every year for the next 20 years. After the trees are cut, the land on which the trees stood can always be sold for $200 an acre. The interest rate is 10%.

When should the trees be cut to maximize the present value of the payments received for trees and land?