The 130 juniors at Smithers High School are taking a class trip. Three buses will be taking the students and chaperones to their destination, and each bus can hold up to 45 people. The first bus will be filled to capacity, followed by the second and third buses. The function f(x) describes the total number of people on the first bus, where x is the number of minutes spent loading the bus. If the first bus is boarded at a rate of 15 people per minute, what is the domain of the function? D= { < x