Sand falls from a hopper at a rate of 0.4 cubic meters per hour and forms a conical pile beneath. Suppose the radius of the cone is always half the height of the cone.

(a) Find the rate at which the radius of the cone increases when the radius is 4 meters.

I got (a) to be 1/(64pi)

(b) (b) Find the rate at which the height of the cone increases when the radius is 4 meters.

My roomate says I am getting this wrong but he just left.

Thanks, in advance.