a detailed answer to all 3 questions would be greatly appreciated!!

6. A recent advertisement in the financial section of a magazine carried the following claim: "Invest your money with us at 10 percent, compounded quarterly, and we guarantee to double your money sooner than you imagine." How long would it take to double your money? 2pts 7. How much money should you invest each year (at the end of each year) in order to accumulate $1,000,000 for retirement 50 years from now, if you can invest your money at 6%? 2 pts a 8. What is the present value of a 4-year annuity due with annual payments of $200, evaluated at a 13 percent interest rate? 2pts