You are considering two options. One is an electric engine powered car, and it would take $45,000 to purchase the car. Besides, you need to change battery every 6 year. The cost of new battery is $6,000. The other is a gasoline engine car, which cost $20,000 initially. The annual maintenance cost for gasoline engine car is $3,000, and the fuel cost per mile is $0.12. On the other hand, it cost $0.04/mile for electric powered car, and annual maintenance cost is $5000. At 12% interest rate, compounded monthly, and useful life of $5,000 for electric car (without buying new battery at the end of year 12), and $3,000 for gasoline car,

a) Calculate the annual total cost of ownership,

b) Which car to buy? Why?