Jawapan

2016-05-30T23:07:04+08:00
Each = 25 min ,
another = 40 min ,
together = 6 a.m. ,

40 min - 25 min = 15 min ,
40 min + 15 min = 55 min ,
25 min + 15 min = 40 min ,
6 : 15 a.m. (rang) ,

every 15 minutes it would rang together