At what rate is the distance between the two cars increasing 2 hours after car B leaves the intersection?

At what rate is the distance between the two cars increasing 2 hours after car B leaves the intersection? 4. Sand is being dumped from a conveyor belt at a rate of 12 Cubic feet per minute. The coarseness of the sand is such that it forms a pile in the shape of a cone with the radius of the base always 1/2 the height. How fast is the height increasing when the pile is 15 feet high?