Acceleration of mass on a spring

[futurept]

Homework Statement

A 2.0 kg mass is placed on top of a vertical spring, which compresses to a new equilibrium position; the spring is then compressed from this new equilibrium position by a distance of 0.05 m. What will be the acceleration of the mass just after the spring is released from this position?

I don't really know where to start. The only equation I can find that is relevant is F= -kx. But no spring constant is given. Any help please?

 

[futurept]

All I'm really asking for here is the starting point. I think I can do it from there, I just don't know where to get started from.

 

[fluidistic]

It doesn't matter if they don't give you a numerical value for k. It means your answer will depends of k.

 

[futurept]

So what do I do then. Consider that k=mg/x? then from there I can find the force. Then set that value to F=ma?