9. A set B is closed under operation op iff V m, n EU, (me Bane B) m op n e B. Consider the following sets and arithmetic operations +, 35, l. For each set, indicate ALL arithmetic operations under which the set is closed. If a set is not closed under any operations, write NONE. (3 points each) a. The set of negative real numbers. b. The set of positive rational numbers. c. The set of odd numbers. d. The set of even numbers. e. The set {-1, 1} f. The set {-1, 0, 1}