Jawapan

2016-03-04T08:45:26+08:00
Ali = -4.5+2.5= - 2
2016-03-04T13:24:12+08:00
Ahmad = -4.5 m
ali = +2.5 m

kedudukan ali
= -4.5 +2.5
= -2 m

maka, ali berada 2 m di bawah paras tanah