A spring hanging vertically obeying Hooke's law extends by $2\mathrm{.}00$ cm when it supports a mass of $2\mathrm{.}50$ kg $.$ Given that the spring is $12\mathrm{.}0$ cm long when supporting no weight, how long will it be if it supports a mass of $10\mathrm{.}0$ kg $?$

$18\mathrm{.}0$ cm

$8\mathrm{.}0$ cm

$14\mathrm{.}0$ cm

$20\mathrm{.}0$ cm

$12\mathrm{.}0$ cm