Low-energy lightbulbs typically cost $3.75, have a life of nine years, and use about $1.85 of electricity a year. Conventional lightbulbs are cheaper to buy, for they cost only $.55. On the other hand, they last only about a year and use about $6.85 of energy. a. If the real discount rate is 6%, 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