Low-energy lightbulbs typically cost $4.40, have a life of nine years, and use about $2.50 of electricity a year. Conventional lightbulbs are cheaper to buy, for they cost only $.68. On the other hand, they last only about a year and use about $7.50 of energy. a. If the real discount rate is 7%, what is the equivalent annual cost of the two products? (Do not round intermediate calculations. Enter your answers as a positive value rounded to 2 decimal places.) b. Which product is cheaper to use? Low-energy lightbulbs Conventional lightbulbs