A 30 year-old man intends to retire in 30 years. he would like to be certain of having an annual income of 15,000 $ per annum when he retires. and he anticipates that he could live for 20 years following retirement. assuming an average annual interest rate of 5 % for the next 50 years, how much money should the man deposit to the bank in saving annually over the next 30 years?