A plant manager wants to know the present worth of the maintenance costs for a reconditioned assembly line. An industrial engineer, who designed the system, estimates that the maintenance costs are expected to be zero for the first three years, $2000 in year four, $2500 in year five, and amounts increasing by $500 each year through year 10. At an interest rate of 8% per year compounded semiannually, the value of n to use in the PG equation is:

a. 7

b. 8

c. 10

d. 14