I’m not sure how to do this question

Find the surface area of the prism formed by the net

At a sand and gravel plant, sand is falling off a conveyor and onto a conical pile at a rate of 16 cubic feet per minute. the diameter of the base of the cone is approximately three times the altitude. at what rate is the height of the pile changing when the pile is 12 feet high? (hint: the formula for the volume of a cone is v = 1 3 πr2h.)

What is the average rate of change for this function for the interval from x=2 to x=4 ?