Answer
There are images from both $O$ and $I_1$ in the more distant mirror, $\mathrm{M}_2$ : an image $I_2$ located at $30 \mathrm{~cm}$ behind $\mathrm{M}_2$. Since $O$ is $30 \mathrm{~cm}$ in front of it, $I_2$ is $60 \mathrm{~cm}$ from $O$. This is the second smallest distance between the object and an image of the object.
Work Step by Step
There are images from both $O$ and $I_1$ in the more distant mirror, $\mathrm{M}_2$ : an image $I_2$ located at $30 \mathrm{~cm}$ behind $\mathrm{M}_2$. Since $O$ is $30 \mathrm{~cm}$ in front of it, $I_2$ is $60 \mathrm{~cm}$ from $O$. This is the second smallest distance between the object and an image of the object.
