Please solve carefully!! Thank you

A company has purchased equipment (for $55,000) that will reduce materials and labor costs by $14,000 each year for N years. After N years, there will be no further need for the machine, and because the machine is specially designed, it will have no MV at any time. The IRS, however, has ruled that the company must preciate the equipment on a SL basis with a tax life of four years. If the effective income tax rate is 37%, what is the minimum number of years the company must operate the equipment to earn 9% per year after taxes on its investment? Click the icon to view the interest and annuity table for discrete compounding when the MARR is 9% per year. Your firm must operate the equipment for minimum years to earn 9% per year after taxes on its investment. Round to the nearest whole number