Grain is emptying from the bottom of a funnel-shaped hopper at a rate of 1.2m3/min. If the diameter of the top of the hopper is 5m and the sides make an angle of 30o with the vertical, determine the rate at which the level of grain in the hopper is changing, when it is half the height of the hopper. P.S. (I am supposed to use implicit differentiation to find rates of change) The answer is -0.24m/min. I can't get it!!