RST Corporation is considering two projects, R and S:

Year	Project R Cash Flow ($)	Project S Cash Flow ($)
0	-80,000	-100,000
1	25,000	30,000
2	35,000	40,000
3	45,000	50,000
4	55,000	60,000
IRR	20%	22%

The discount rate is 10%.

a) Calculate the NPV of both projects. b) Decide which project should be undertaken. c) Discuss why NPV is preferred over IRR in certain scenarios. d) Evaluate how project duration influences the investment decision.