Problem Solved: Pump Discharge Rate - Wastewater Math

http://americanwatercollege.org This question comes from the California Wastewater grade 3 certification exam sample questions that can be found here: http://www.swrcb.ca.gov/water_issues/... The problem reads: A pump was noted to lower the level in a basin by 10 feet in 12 minutes and 20 seconds while a steady flow rate of 180 g.p.m. was entering the basin. The basin diameter was 12 feet. What was the discharge rate of the pump expressed in gallons per minute