One of the largest car dealers in the city advertises a 3-year-old car for sale as follows. Cash price $13,750, or a down payment of $1375 with 45 monthly payments of $361.23. Sharon bought the car and made a down payment of $2000. The dealer charged her the same interest rate used in his advertisement. What is the monthly interest rate? How much will Sharon pay each month for 45 months? What effective interest rate is being charged?