FCC is planning to invest in a new machine. The machine will generate $29,000 a year in sales with net annual cash flow of $ 15,600. The machine is priced at $79,000 . What is the payback period for this investment (round the final answer to the nearest one decimal place, i.e. 10.25 would be 10.3 or 12.97 would be 13.0 ?