Train A and B of equal lengths of 120m are moving towards a 300 m long tunnel. Train B enters the tunnel after 30 seconds when train A entered the tunnel. Train A crosses the tunnel in one minute. If both of them leave the tunnel at the same time, then what is the speed of train B?
1
23 m/s
2
20 m/s
3
14 m/s
4
15 m/s
5
10 m/s