Time value of money

Jill Grant is 22 years old (at T=0) and is planning for her retirement at age 63(t=41). she plans to save 2000 per year for 15 year(t=1 to t=41 to t=15). she wants to have retirement income of 100000 per for 20 years, with first retirement payment starting at 1=41. h0w much must grant save each year from t=16 to t=40 in order to achieve her retirement goal? Assume she plans to invest in diversified stock and bond mutual fund that will earn 8 percent per year on average?