Motion in a Straight Line

Two balls A and B are placed at the top of 180m tall tower. Ball A is released from the top at t=0s. Ball B is thrown vertically down with an initial velocity 'u' at t=2s. After a certain time, both balls meet 100m above the ground. Find the value of ' u ' in ms−1⋅[. use .g=10ms−2] :