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