A ball of mass $200 \mathrm{~g} rests on a vertical post of height 20 \mathrm{~m}. A bullet of mass 10 \mathrm{~g}, travelling in horizontal direction, hits the centre of the ball. After collision both travels independently. The ball hits the ground at a distance 30 \mathrm{~m} and the bullet at a distance of 120 \mathrm{~m} from the foot of the post. The value of initial velocity of the bullet will be (if g=10 \mathrm{~m} / \mathrm{s}^{2}$) :