Water flows from a faucet into a bathtub at a constant rate of 9 gallons of water pouring out every 2 minutes. The bathtub is initially empty, and its plug is in.
a.) Determine the rule that describes the volume of water in the tub in gallons (g) as a function of time in minutes (m) and write the rule as an equation.
b.) If the tub can hold 72 gallons of water, how long will it take to fill the tub? Round to the nearest minute.