Econo-Cool air conditioners cost $480 to purchase, result in electricity bills of $330 per year, and last for five years. Luxury Air models cost $680, result in electricity bills of $280 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.)