Spam (2,08 8. [1/2 Points] DETAILS BERRFINMATH1 2.2.007. MY NOTES Use the "rule of 72" to estimate the doubling time (in years) for the interest rate, and then calculate it exactly. (Round your answers to two decimal places.) 4% compounded annually, "rule of 72" x yr exact answer 18 yr Additional Materials eBook Show My Work (Optional) 9. [0/1 Points] DETAILS BERRFINMATH1 2.2.009. Find the effective rate of the compound interest rate or investment. (Round your answer to two decimal places.) 20% compounded monthly. [Note: This rate is a typical credit card interest rate, often stated as 1.7% per month.] X% Enter a number Additional Materials eBook dtv MacBook Air MY NOTES