You started an investment account 10 years ago with $1900, and it now has grown to $8600. a. What annual rate of return have you earned (you have made no additional contributions to the account)? b. If the investment account earns 15% per year from now on, what will the account's value be ten years from now? a. The annual rate of return is %. (Round to two decimal places.) b. The account's value will be $. (Round to the nearest dollar.)