A $2\mathrm{.}0-$kg block sliding on a horizontal frictionless surface is attached to one end of a horizontal spring $(k=200\frac{N}{m})$ which has its other end fixed. If the block has a speed of $4\mathrm{.}0\frac{m}{s}$ as it passes through the equilibrium position, what is its speed when it is $20$ cm from the equilibrium position?

$(1)2\mathrm{.}6\frac{m}{s}$

$3\mathrm{.}1\frac{m}{s}$

$3\mathrm{.}5\frac{m}{s}$

$1\mathrm{.}9\frac{m}{s}$

$2\mathrm{.}3\frac{m}{s}$