(3) Let m be a positive integer. (a) Prove that Z/mZ is acommutative ring. (b) Prove that if m is composite, then Z/mZ isnot a field.
(4) Let m be an odd positive integer. Prove that every integeris congruent modulo m to exactly one element in the set of evenintegers {0, 2, 4, 6, , . . . , 2m− 2}
