The graph below models the value of a $20,000 car t years after it was purchased. Value of Car A graph titled Value of Car has years on the x-axis and Dollars on the y-axis. A line curves down and goes through points (0, 20,000), (4, 10,000), and (14, 2,000). Which statement best describes why the value of the car is a function of the number of years since it was purchased?