A spring with a spring constant of $1200\frac{N}{m}$ has a $55-$gball at its end. The energy of the system is $4\mathrm{.}0J.$

The amplitude $A$ of vibration is $8\mathrm{.}2*10^-2$ m

The maximum speed of the ball is $12$ m$/$s$.$

What is the speed when the ball is at a position $x=+\frac{A}{2}?$

Express your answer with the appropriate units.

$v=$