Given the following data, calculate the payback period for the proposed investment in a digital mammography scanner by Rockpile Radiology:

Equipment cost: $300,000

Cash Inflow year 1: $50,000

Cash Inflow year 2: $75,000

Cash Inflow year 3: $100,000

Cash Inflow year 4: $125,000

Cash Inflow year 5: $150,000

Corporate cost of capital: 6.5%

Disposal value: $30,000