LED lights bulbs typically cost $3.50, have a life of 9 years, and use about $1.60 of electricity a year. Conventional light bulbs are cheaper to...

LED lights bulbs typically cost $3.50, have a life of 9 years, and use about $1.60 of electricity a year.

Conventional light bulbs are cheaper to buy, for they cost only $.50.

On the other hand, they last only about a year and use about $6.60 of energy.

If the real discount rate is 5%, what is the cost of the two products over 9 years? Which one is better cost-wise?

Cash flow 

1) LED lights

Cash flow from LED lights 

CF0, CF1, ... CF9 = ??

Present value = ?? 

2) Conventional lights

Cash flow till year 9

CF0, CF1, ... CF9 = ??

Present value = ??