Since addition modulo n and multiplication modulo n of integers are commutative . So, the ring is a commutative ring.
Suppose
Then, , where m is the reminder obtained when ab, ba is divided by 6 and
ab
Also, , where n is the reminder obtained when is divided by 6 and
Hence, is a commutative ring
A ring is a field if its every element has an inverse.
As
but
So, 2 and 3 are zero divisors and do not have inverse .
So, is not a field.