"A new delivery truck is available for $215,000. O&M costs are $20,000 each year for the first five years, $30,200 in year six, $48,000 in year seven, and $76,300 in year eight. Salvage values are estimated to be $187,000 after one year and will decrease at the rate of 20% per year thereafter. At a MARR of 10%, determine the economic service life of the truck. Enter your answer as an integer from 1 to 8."