$$5800$ is invested for $10$ years at the following interest rates: $=8\mathrm{.}5\%$ for the first $4$ years; $=7\%$ for the next $4$ years $($following the first $4$ years$)$; and $=4\%$ for the final $2$ years.a$)$ Determine the accumulated value of the investment after $10$ years.Answer: $b$)$ What equivalent nominal rate, $,$ was earned over the $10-$year period?Answer: $\%$