A typical muscle fiber is 2 . 0 2 . 0 cm long and has a cross - section area of 3 . 1

 A typical muscle fiber is $2\mathrm{.}0$ cm  long and has a cross$-$section area of $3\mathrm{.}1$ times $1\mathrm{0^}9$m$.$ When the muscle fiber is stimulated, it pulls with a force of $1\mathrm{.}2$ mN$.$ What is the work done by the muscle fiber as it contracts to a length of $1\mathrm{.}4$  cm$?$