Problem 4: You are planning your retirement in 30 years and you have saved already $20,000. Assume you plan to save an additional $1200 at the end of each of the next 30 years to the account. If the account earns a return of 5 percent per year over the next 30 years, how much will you have in the account when you retire? Problem 5: You currently have $10,000 in a stock account. If the stock account earns a return of 8 percent per year over the next 30 years, how much will you have in the stock account when you retire? Problem 6: Assume you will transfer your money from the two accounts above into a combined retirement account that earns 4 percent interest annually. Your plan is to withdraw an equal amount from your combined account at the end of each year for the next 20 years and then have nothing left. How much can you withdraw each year in your retirement