I only need the answer to part D, comment if you need more information to solve. Please help me out!
Your family plans to buy a new air conditioner. They can buy the Super Cool X1400 for 800, or they can buy the Efficient Energy X2000 for 1200. Both models will cool your home equally well, but the Efficient Energy model is less expensive to operate. The Super Cool X1400 will cost 60 per month to operate, while the Efficient Energy X2000 costs only 40 per month to operate.
Part D: Figuring your family will only use the air conditioner for four months each year, how many years will you have to wait to start saving money overall?