A pulley of mass m and moment of inertia I about its axis is suspended as shown in the diagram. The spring has spring constant 'k' and the string does not slip over the pulley. Find the extension in the spring under equilibrium condition.
1
\(\frac{{2k}}{{mg}}\)
2
\(\frac{{k}}{{mg}}\)
3
\(\frac{{mg}}{{k}}\)
4
\(\frac{{mg}}{{2k}}\)