Whats the rate ?

Helium is pumped into a spherical balloon at a constant rate of 4 cubic feet per second. How fast is the radius increasing after 2 minutes? At what time (if any) is the radius increasing at a rate of 120 feet per second? The radius is increasing at a rate of ft/sec. (Type an integer or a decimal. Do not round until the final answer. Then round to four decimal places as needed.)