Erika and Kitty, who are twins, have just received $30,000 each for their 25th birthday. Each sister plans to make a $5,000 annual contribution to her retirement fund on her birthday, beginning a year from today. Erika opened an account with a fund that provides a 6% return per year. Kitty invested in fund that provides a 20% return per year. a. How old will each sister be when she becomes a millionaire? b. How large should Erikas annual contributions have to be for her to become a millionaire at the same age as Kitty?