Engineering Economy 7th Edition by Leland Blank ,Anthony Tarquin

Exercise 71

A tractor has a first cost of $40,000, a monthly operating cost of $1500, and a salvage value of $12,000 in 10 years. The MARR is 12% per year. An identical tractor can be rented for $3200 per month (operating cost not included). If n is the minimum number of months per year the tractor must be used in order to justify its purchase, the relation to find n is represented by:
A) 40,000( A / P ,1%,10) 1500 n + 12,000( A / F ,1%,10) = 3200 n
B) 40,000( A/P ,12%, 10) 1500 n + 12,000( A / F ,12%,10) = 3200 n
C) 40,000( A / P ,1%,120) 1500 n + 12,000( A / F ,1%,120) = 3200 n
D) 40,000( A / P ,11.4%,10) 1500 n + 12,000( A / F ,11.4%,10) = 3200 n