A couple will retire in 40 years; they plan to spend about $21,000 a year (in current dollars) in retirement, which should last about 20 years. They believe that they can earn a real interest rate of 7% on retirement savings. a. If they make annual payments into a savings plan, how much will they need to save each year? Assume the first payment comes in 1 year. Note: Do not round intermediate calculations. Round your answer to 2 decimal places. b. How would the answer to part (a) change if the couple also realize that in 15 years they will need to spend $51,000 on their child's college education? Note: Do not round intermediate calculations. Round your answer to 2 decimal places