Please tell me how to solve the given related rates problem

1)

You are creating the body of snowman (a sphere). The volume changes at a rate of 16 in3/min.

When the radius in 8 inches, how fast is the surface area changing in in2/min?

(Find how fast the radius is changing first)

2)

The bottom of a 15-foot ladder is sliding away from a building at 2ft/min (so that the top of the ladder slides down the building). When the bottom of the ladder is 10feet from the building, how fast is the top of the ladder sliding down?