Continue the preceding example. If the lease monthly payment is $40 less than the finance agreement monthly payment and the difference is used to pay down a credit card debt at a monthly rate of 1.333% (16% APR), the following calculation, incorporating both the initial payment difference and the monthly payment difference, would be required.

 

Col. A	Col. B	Col. C	Col. D	Col. E	Col. F
Time period	Initial lease payment difference plus monthly payment difference	Accumulated interest from previous months	Total payment difference plus earnings	Interest saved (Col. D × 1.333%)	End-of-month total savings (D + E)
Beginning	$800.00	0.00	800.00	10.67	810.67
Month 2	$840.00	10.67	850.67	11.34	862.01
Month 3	$880.00	22.01	902.02	12.02	914.03
~	~	~	~	~	~
Month 36

If the interest rate benefit were different in any month, the monthly interest rate multiplier in column E would change for that month. You would have to project the return you would receive on the payment difference over the full term of the lease and financing agreement to accurately include this economic benefit in the model.