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5. Mary is saving for a new car. She invests $ 4000 into an account that pays 4 % interest a year and is compounded quarterly. How long will it take her investment to double? 6. Sabine is planning to buy an office in 5 years. She wants to invest $ 20,000 now and hopes to have $ 30,000 to buy the ofce. What interest rate would she need in her investment if compounded monthly? 7. Virginie stops at a coffee shop every work day (20 times a month) to drink a $ 4.75 latte. After studying investment, she decides to skip the latte and instead invest the same amount, at the end of each month, in an annuity paying 5.7 % compounded monthly, if she continue this for 40 years, how much will the annuity be worth? How much interest will Virginie earn over the 40 years? 8. Suppose $ 1500 is deposited at the end of each year for the next 6 years in an account paying 8 % interest compounded annually. Find the future value of this annuity