let a = {1,3,5,7,9}, b= {3,6,9}, and c= {2,4,6,8}.
which one of the following is correct, is answer a or b correct?
a)
(a ? b) ? c = {2,3,4,6,8, 9}
b)
a ? (b ? c) = {3,5,6,7,9}