The traffic lights at four different road crossings change after every 15 sec, 18 sec, 27 sec and 30 sec respectively. If they all change simultaneously at 6 : 10 : 00 hours, then at what time will they again change simultaneously?
1
6 : 14 : 30 hours
2
6 : 40 : 00 hours
3
6 : 14 : 00 hours
4
10 : 40 : 00 hours