A Spherical Party Balloon Is Being Inflated by Helium Pumped $V = \frac { 4 } { 3 } \pi r ^ { 3 }$

Multiple Choice

A spherical party balloon is being inflated by helium pumped in at a rate 3 cubic feet per minute. How fast is the radius growing at the instant when the radius has reached 1 foot Round your answer to the two decimal places.
The volume of a sphere of radius r is

$V = \frac { 4 } { 3 } \pi r ^ { 3 }$ .

A) 0.72 feet per minute
B) 0.76 feet per minute
C) 0.14 feet per minute
D) 0.64 feet per minute
E) 0.24 feet per minute