Need to solve in Excel.

John Wayne is 50 years old and plans to retire in 20 years. His new employer provides 401K retirement plan and he plans to accumulate $1,000,000 in his retirement account by age of 70. Use Excel to answer the following questions. a- How much he has to contribute per year at return of 7% per year to reach his retirement goal. b- Redo part (a) if john decides to increase his contribution 0.50% per year over 20 years. C- Redo part (a) if the yearly return for the first 10 years is 7% and last 10 years is 9%