Let `A` be the set of all students of a boys school. Show that the relation `R` on `A` given by `R={(a ,\ b): a` is sister of `b}` is empty relation and `R^(prime)={(a ,\ b):` the difference between the heights of `a` and `b` is less than 5 meters} is the universal relation.

Explanation

A= All students in boys school

R={(a,b):a is sister of b}

As there is no a in A as there is no girl in boys school,
we can say that R is an empty relation.




R'={(a,b):the difference between heights of a and b is less than `5` meters}

As both a and b are related to each other in set A, R' is universal relation.