single-stage centrifugal fire pumps use a single intake impeller and a simple casing to provide flow capacities up to: select one: a. 500 gpm (2 000 l/min). b. 1,000 gpm (4 000 l/min). c. 2,250 gpm (9 000 l/min). d. 3,500 gpm (14 000 l/min).