This question is too complex for me and I don't know where to start. For now, I think maybe I should try to show that, since N is recursive, then A is creative iff $A\otimes N$ is creative so that I can show that $A\otimes N$ must not be creative, however even this proof is quite confusing to me.
Any idea will be deeply appreciated!
By the way, here $A\otimes B$ means {$(a,b)| a\in A$ and $b\in B $}.