The volume V of a growing spherical cell is , where the radius is measured in micrometers (1 µm = m). Find the average rate of change of V with respect to r when r changes from 3 to each of the following. (Round your answers to one decimal place.) 1) 3 to 6µm
2) 3 to 4µm
3) 3 to 3.1µm
4) Find the instantaneous rate of change of V with respect to r when r=3µm.