For each of the following sets G and operations * state, with justification, whether or not (a) * is a closed binary operation (b) is associative, (c) there is an identity element, (d) which elements have an inverse, (e) Gunder is a group. (i) G = {x ER : x # 0} and x x y = 3xy. (ii) G = R and x x y = Vx3 + y3. (iii) G = {x E R : x 2 0} and x x y = |x - yl