Econo-Cool air conditioners cost $300 to purchase, result in electricity bills of $150 per year, and last for five years. Luxury Air models cost $500, result in electricity bills of $100 per year, and last for eight years. The discount rate is 21%. a. What is the equivalent annual cost of the Econo-Cool model? (Do not round intermediate calculations. Round your answer to 2 decimal places.) b. What is the equivalent annual cost of the Luxury Air model? (Do not round intermediate calculations. Round your answer to 2 decimal places.) c. Which model is more cost-effective? d. If the inflation rate is expected to be 10% per year for the foreseeable future. What is the equivalent annual cost of the Econo-Cool model and Luxury Air model? (Do not round intermediate calculations. Round your answer to 2 decimal places.)