Apex Corp. is planning to buy production machinery costing $100,000. This machinery's expected useful life is five years, with no residual value. Apex uses a discount rate of 10% and has calculated the following data pertaining to the purchase and operation of this machinery: Year Estimated annual net cash inflow 1 $60,000 2 30,000 20,000 20,000 20,000 3 4 5 The payback period is