Which of the following are groups? Justify your answers.(a) The set 3Zof integers that are multiples of 3, under addition. Thatis:3Z={3n|nZ}(b)R\{0}under the operationab=|ab|, for alla, bR\{0}(c) The set{1,1}under multiplication(d) The set of all pairs (x, y) of real numbers, under the operation(x, y)(z, w) = (x+z, yw)(e)R\{1}under the operationab=a+bab, for alla, bR\{1}(f)Zunder the operationab=a+b1, for alla, bZ4. For each case in Exercise 3 above, which you have shown to be a group,determine whether or not it is abelian.