
Lenny D. answered 12/14/19
Former professor of economics at Tufts University
The question becomes whether the present value of the lease payments is Greater or less than the purchase price The Present value of a constant steam of Payments is PV=PMT*K(i,t) where PV = Present Value, PMT = Payment and k is the multiplier which is a decreasing function of i and an increasing function of t (the higher the interest rate the lower the PV and the more payments the higher the PV.
K is given as K=(1/i)(1 -(1/(1+i))t) Here we have 3 years of monthly payments (t=36) and the periodic or monthly interest rate is 18%/3 = 1.5%) so K = (1/0.015)(1 - ((1/(1.015))36) = 27.66
The monthly lease payment is 2,800 so the PV = 27.66*2,800=77,449.91. So it is more than $10,000 cheaper to lease.
Hope this helps. If you need help studying for finals please reach out.