A new restaurant is being built with a main kitchen and a separate bar area. The plans call for a single large grease interceptor to serve both areas. The combined fixture discharge from the kitchen (sinks, dishwashers, etc.) is 45 fixture units. The bar area has a three-compartment sink and a pre-rinse spray valve, totaling 6 fixture units. What is the minimum required flow rate, in gallons per minute, for sizing this interceptor?