A 12.8 gram bullet embeds itself in a 2.370 kg block on a horizontal frictionless surface which subsequently collides with a spring of stiffness 487 N/m. The maximum compression of the spring is 11.0 centimetres.
a) What was the initial speed of the bullet in m/s?
b) How long did it take for the bullet-block system to come to rest after contacting the spring?