Interest rate $($with changing years$).$ Keiko is looking at the following investment choices and wants to know what annual rate of return each choice produces.

a$.$ Invest $$420\mathrm{.}00$ and receive $$689\mathrm{.}49$ in $8$ years.

b$.$ Invest $$3,000\mathrm{.}00$ and receive $$12,608\mathrm{.}87$ in $16$ years.

c$.$ Invest $$31,230\mathrm{.}76$ and receive $$100,000\mathrm{.}00$ in $22$ years.

d$.$ Invest $$32,017\mathrm{.}36$ and receive $$1,200,000\mathrm{.}00$ in $35$ years.

a$.$ What annual rate of return will Keiko earn if she invests $$420\mathrm{.}00$ today and receives $$689\mathrm{.}49$ in $8$ years?

$\%($Round to two decimal places.$)$