Please explain how to calculate the input rate.

The bathtub theory of operations management is being promoted as the next breakthrough for global competitiveness. The factory is a bathtub with 60 gallons of capacity. The drain is the outlet to the market and can output 2.5 gallons per hour when wide open. The faucet is the raw material input and can let material in at a rate of four gallons per hour. Now, to test your comprehension of the intricacies of operations (assume the bathtub is empty, to begin with):

a-1. What is the maximum rate (gallons per hour) at which the market can be served if all valves are set to maximum? (Round your answer to 1 decimal place.)

a-2. If the faucet is running at maximum and the drain is wide open, in how many hours will the bathtub completely fill and start to overflow? (Round your answer to 1 decimal place.)

b. Suppose that, instead of a faucet, a four-gallon container is used for filling the bathtub (assume a full container is next to the tub, to begin with); it takes two hours to refill the container and return it to the bathtub. What is the average output rate (gallons per hour)? (Round your answer to 1 decimal place.)