Maria estimates she will need income from savings and investments for 20 years after she retires at age 67, based on actuarial tables for life expectancy. She is 47, and so has 20 years to save. She estimates her adjusted expenses in retirement will be about $35,000 a year after inflation if she is very frugal. She estimates her Social Security will cover about $12,000 a year, so her nest egg must provide $23,000 per year. Assuming a 5% average rate of return, roughly how much should she save or invest each year to be sure of having enough to retire