Iron Chef Ovens cost $3000 to purchase, result in electricity bills of $250 per year, and last for 5 years. Luxury Ovens cost $5000, result in electricity bills of $150 per year, and last for 8 years. The discount rate is 15%.

a. What are the equivalent annual costs for two models? and how to use the calculator?

b. Which model is more cost-effective?