Let $\alpha$ be an atom or a list, and let $\lambda$ be a list. Define the function remove by:
remove $(\alpha, \lambda)=[$ if $\lambda=()$ then ( )
else if $\operatorname{head}(\lambda)=\alpha$ then remove $(\alpha, \operatorname{tail}(\lambda))$
else $\operatorname{cons}(\operatorname{head}(\lambda), \operatorname{remove}(\alpha, \operatorname{tail}(\lambda)))$ ].
Let member be the function defined in the previous exercise. Prove that member $(\alpha$, remove $(\alpha, \lambda))=()$.