Wrk,energy,power

A car of mass 800 kg is moving along a straight horizontal road. The engine of the car is working at a constant power of 20kW. The frictional resistance to motion has magnitude 500N. At time t s the speed of the car is v m/s. Show tha 8(dv/dt) = (5(40-v))/v. Given that this differential equation may be written in the form dt/dv=64/(40-v)-(8/5), find, to the nearest 0.1 s, the time taken for the speed of the car to increase from 10 m/s to 15 m/s.