Also find: Using the useful life of the machine rounded to the nearest year, the total profit accumulated during the useful life of the machine is_________(Round to the nearest dollar as needed.)

The total accumulated costs C(t) and revenues R(t) (in thousands of dollars), respectively, for a photocopying machine satisfy c'(1 = - 15 and R'(1) = 7te- P where t is the time in years. Find the useful life of the machine, to the nearest year. What is the total profit accumulated during the useful life of the machine? The useful life of the machine is year(s). (Round to the nearest year as needed.)