relations,functions and binary operation

In which of the following sets is subtraction a binary operation? O Integers and Rational Numbers O Whole Numbers O Integers O Whole Numbers and Integers The binary table below is commutative but not associative abcd a abcd bb cda ccdab d d abc False True * abcd a abcd bb cda da d da bc (a * b) * c= a * (b*c) False True If a * b = 2a - 6b, what is 7 * 9? O -40 12 O -68 O 72