One horse pulls with a force of X N, a cart of mass 800 kg along a horizontal road at constant speed. Three horses, each pulling with a force of X N, give the cart an acceleration of 0.8m/s^2. Find the time it wd take for 2 horses to increase the speed of the cart from 2m/s to 5m/s, given that each horse pulls with a force of X N and that the resistance to motion has the same constant values.