The diameter of a spherical bob is measured using a vernier callipers. 9 divisions of the main scale, in the vernier callipers, are equal to 10…

The diameter of a spherical bob is measured using a vernier callipers. $\displaystyle 9$ divisions of the main scale, in the vernier callipers, are equal to $\displaystyle 10$ divisions of vernier scale. One main scale division is $\displaystyle 1$ mm . The main scale reading is $\displaystyle 10$ mm and $\displaystyle 8^{\text {th }}$ division of vernier scale was found to coincide exactly with one of the main scale division. If the given vernier callipers has positive zero error of $\displaystyle 0.04$ cm, then the radius of the bob is \_\_\_\_ $\displaystyle \times 10^{-2} \mathrm{~cm}$.