Consider the following two mutually exclusive investment alternatives with given (MARR= 10%)

Year	Project A1	Project A2
0	-15,000 $	-20,000 $
1	7,500 $	8,000 $
2	7,500 $	15,000 $
3	7,500 $	5,000 $
i*	23.5 %	20 %

a) Find the best alternative of A1 and A2 based on the present worth incremental investment.

b) Find the best alternative of A1 and A2 based on the IRR incremental investment.