Consider a cylinder that is divided into two compartments by a movable piston. Initially, the volume and pressure of oxygen gas in the first compartment are $1$ $Pa$ and $12$ $L$ respectively. And the volume and pressure of oxygen gas in the second compartment are $2$ $Pa$ and $4$ $L$ respectively. When the system reaches equilibrium, what will be the pressure of the first compartment? Assume that heat can be exchanged through the wall of the cylinder and the piston.

Hint: Do you know Boyle's Law?