Ray Optics

The image of an object approaching a convex mirror of radius of curvature 20 m along its optical axis is observed to move from $\frac{25}{3} \mathrm{~m}$ to $\frac{50}{7} \mathrm{~m}$ in 30 second. The speed of the object in $\mathrm{km} / \mathrm{hr}$ is