Please show your steps and explain with formulas

5-51 Investing for Retirement Monica has decided that she wants to build enough retirement wealth that, if invested at 8 percent per year, will provide her with $3,500 of monthly income for 20 years. To date, she has saved nothing, but she still has 30 years until she retires. How much money does she need to contribute per month to reach her goal? (LG5-4, LG5-9)