How to find the incremental return of analysis by hand instead of using excel. I know how to use XIRR function in excel, however, I am confused about how to do it without using excel. Please help me step by step. Here is an example below where I need to use this method.

Google is evaluating three companies to buy a motor from. The motor will be used for the next 5 years. If only one machine can be chosen, do nothing is an alternative and the minimum attractive rate of return is 16.5% which motor should be chosen if any? (use the incremental rate of return analysis.)

	Alternative
	Large	Medium	Small
First Cost	225,000	127,000	74,000
Annual benefit	78,000	44,000	29,000
Maintenance and Operating Cost	39,000	12,000	8,500
Salvage value	16,500	6,800	3,100

Thank you