Please help, I keep arriving at the same wrong answer of "7 years"

Milliken uses a digitally controlled dyer for placing intricate and integrated patterns on manufactured carpet squares for home and commercial use. It is purchased for $400,000. Its market value will be $310,000 at the end of the first year and drop by $46,000 per year thereafter to a minimum of $30,000. Operating costs are $20,000 the first year, increasing by 5% per year. Maintenance costs are only $8,000 the first year but will increase by 37% each year thereafter. Milliken's MARR is 18%.

Determine the optimum replacement interval for the dyer. "______ years"

(The answer is not 7 years, this is what I have gotten previously but it is incorrect.)