A $250$ g object on a frictionless, horizontal lab table is pushed against a spring of force constant $35\frac{N}{c}m$ and then released. Just before the object is released, the spring is compressed $12\mathrm{.}0$ cm $.$ After the object is released, how fast is the object moving when it has half of the spring's original stored energy?

A$.5\mathrm{.}6\frac{m}{s}.$

B$.10\frac{m}{s}.$

C$.15\frac{m}{s}.$

D$.12\frac{m}{s}.$