You have an investenent acoount that stated with $4,00010 years ago asd which now has grown to $12,000 a. What annual rate of retum heve you eamed (you have made no addtional contributions to the account? b. If the savings bond earns 15% per year from now on, what wil the account value be 10 years from now? a. What annual rate of retum have you earned (you have made no additional contributions to the accounty? Vour annual rate of return is \%. (Round to two decimal places.)