An oil refinery uses a cracking tower to produce various petroleum products from crude oil. Determine the crude oil supply in gallons per minute necessary to maintain steady production. Compare total input and output in gallons per minute.

Light oil 250 gpm s.g. =0.81 Grease 15 gpm s.g. = 0.92 Crude oil s.g.= 1.12 Gasoline 620 gpm s.g. = 0.72 Kerosene 78 gpm s.g. = 0.8 Heavy oil 115 gpm s.g.=0.89 Heavy bottom 40 gpm s.g. = 1.2