3) A mine cart weighing 1500 kg and carrying 9000 kg of nely crushed ore rolls from rest clown a slope 300 m long, inclined 30 below the horizontal. Unfortunately, the mine cart has a hole in the bottom, so that the ore leaks out at the rate of 300 kg/ s. a) Derive the differential equation describing the motion of the mine cart. b) How much ore is left in the mine cart when it reaches bottom of the slope