show me equation please

Marco is plans to retire in 21 years. He wants you to assume he will be retired for 17 years before he dies. You calculated that Marco needs $1,406,876 as a lump sum at the beginning of retirement. Use an investment return of 6 percent and an inflation assumption of 1.3 percent. How much money will he need to save monthly to have this amount when he begins retirement? (Round the final answer to 2 decimal places)