At time t = 0 the pool is empty. At time t = 6 hours the pool is full. Once you have a function that represents the amount of water in the pool, you should be able to put any value for t in the domain 0 <= t <= 6 to find the amount of water in the pool. t can be any real number such as: 1, 1.5, 2.8, 3.6589, etc. So all real numbers from 0 to 6 hours.