Two unknown resistors are connected together. When they are connected in series their equivalent resistance is $15\mathrm{.}0.$ When they are connected in parallel, their equivalent resistance is $3\mathrm{.}33.$ What are the resistances of these resistors?

Question $14$ options:

a$)$

$8\mathrm{.}0$ and $7\mathrm{.}0$

b$)$

$10\mathrm{.}0$ and $5\mathrm{.}0$

c$)$

$11\mathrm{.}7$ and $3\mathrm{.}3$

d$)$

$9\mathrm{.}0$ and $6\mathrm{.}0$