In Exercises 1 through 9, determine whether the binary operation * gives a group structure on the given set. If no group results, give the first axiom in the order $1, 2, 93 from Definition 2.1 that does not hold. 2.1 Definition A group (G, *) is a set G, closed under a binary operation *, such that the following axioms are satisfied: 1: For all a, b, c E G, we have (a * b) * c= a * (b* c). associativity of * $2: There is an element e in G such that for all & E G, e*0 =0*e=*. identity element e for * $3: Corresponding to each a E G, there is an element a' in G such that a * a = a *a=e. inversea' of a 2. Let * be defined on 2Z = (2n | n E Z) by letting a * b = a + b