Riley's car was worth $15.000 at the beginning of 2000 and the value of the car decreased exponentially, decreasing by 19% each year. a. Write a function f that delermines the value of Riley's car (in dollars) in terms of the number of years t since the beginning of 2000. f(t)= b. How many years after the beginning of 2000 was Riley's car worth $6,000? years c. How many years after the beginning of 2000 was Riley's car worth $2,000 ? years