Equipment was purchased for $122,400 and it is estimated to have a $6,000 salvage value at the end of its estimated 8-year life. The equipment is estimated to generate cash inflows of $18,000 each year and will be depreciated by using the straight-line method. How long is the payback period on this investment?

a. 7.3 years

b. 7.6 years

c. 6.5 years

d. 6.8 years