A company is considering the purchase of a new machine for $50,000. Management predicts that the machine can produce sales of $16,200 each year for the next 10 years. Expenses are expected to include direct materials, direct labor, and factory overhead totaling $7,800 per year including depreciation of $4,200 per year. Income tax expense is $3,360 per year based on a tax rate of 40%. What is the payback period for the new machine?