San Diego Enterprises is planning to invest in a five-year project costing $270,000. The project is expected to generate annual cash revenues of $90,000 and annual cash expenses (including depreciation) of $30,000. The estimated residual value is $20,000. The project's payback period is: O a. 4.5 years O b. 5 years O c. 3.25 years O d. 3 years