A new doctor has decided to charge $50 for simple office visits. If a test or an x-ray is needed, the doctor will charge and additional $20 for each test or x-ray. The cost of the doctors visit, f(x), is represented by f(x) = 50 +
20x, where x is the number of tests or X-rays conducted. If the doctor will never require more than 4 tests or X-
rays during a visit, determine the domain and range of that situation.