Thirty years ago, your mother invested $$7,000.$ Today, that investment is worth $$320,714\mathrm{.}11.$ What is the average annual rate of return she earned on this investment?

a

$12\mathrm{.}78$

b

$13\mathrm{.}87$

c

$10\mathrm{.}44$

d

$12\mathrm{.}95$

e

$13\mathrm{.}60$