For each of the two sets of numbers below, determine whether it is a field. if it is a field, just write it is a field. if it is not a field, write it is not a field, state which of the field properties does not hold and give an example showing this (a) f ={a+bv/2 a, bz that is, f is the set of all umbers of the form a+ by/2, where a and b are integers.