A spherical balloon is filled with 4500p cubic meters of
helium gas. If a leak in the balloon causes the gas to escape at the rate of `72pi`
cubic meters per minute, then the rate (in meters
per minute) at which the radius of the balloon decreases 49 minutes after the
leakage began is
(1) `9/7`
(2) `7/9`
(3) `2/9`
(4) `9/2`
A. `(9)/(7)`
B. `(7)/(9)`
C. `(2)/(9)`
D. `(9)/(2)`
