A $10-kg$ block on a rough horizontal surface is attached to a light spring $($force constant $=1\mathrm{.}4k\frac{N}{m}).$ The block is pulled $8\mathrm{.}0$ cm to the right from its equilibrium position and released from rest. The frictional force between the block and surface has a magnitude of $30$ N $.$ What is the kinetic energy of the block as it passes through its equilibrium position? $.$

$4\mathrm{.}5$ J

$2\mathrm{.}1$ J

$6\mathrm{.}9$ J

$6\mathrm{.}6$ J

$4\mathrm{.}9$ J