3.a. According to the Rule of 72, how long will it take $1,000 to double if the interest rate is 8%?

3.b. How long will it take the $1,000 to grow to $16,000? Rule of 72

4.a. What is the value ten years hence of $1,000 invested today at 8% interest, $2,000 invested at the end of year five, and $3,000 invested at the end of year eight?