You are the product actuary for a life insurance company. You have developed a 5-year decreasing annuity that pays $1000 per unit at the end of the first year, $500 at the end of the second year, $333 at the end of the third year, $250 at the end of the fourth year, and $200 at the end of the fifth year. Calculate the Macaulay duration for this annuity given an effective interest rate of 5%