Consider a binary operation * on N defined as a * b = a3 + b3, choose the correct answer :

* is both associative and commutative * is associative but not commutative * is commutative but not associative * is neither commutative nor associative

* is commutative but not associative

$a * b = b * a$ as $a^3+b^3=b^3+a^3$ (commutative true) but $(a * b) * c = (a^3+b^3)^3+c^3$ $a *(b* c)=a^3+(b^3+c^3)^3$ so $(a * b) * c ≠ a *(b* c)$ (Not associative)