Low-energy lightbulbs cost $3.50, have a life of nine years, and use about $1.60 of electricity a

Question:

Low-energy lightbulbs cost $3.50, have a life of nine years, and use about $1.60 of electricity a year. Conventional lightbulbs cost only $.50, but last only about a year and use about $6.60 of energy. If the real discount rate is 5%, what is the equivalent annual cost of the two products?

Discount Rate
Depending upon the context, the discount rate has two different definitions and usages. First, the discount rate refers to the interest rate charged to the commercial banks and other financial institutions for the loans they take from the Federal...