A is running a polyclinic well-equipped with operation theaters and supporting staff. S is a surgeon who makes use of this polyclinic to operate his patients. While operating a patient P, due to the negligence of nurse N (who was a support staff of polyclinic), the surgical knife was left inside the abdomen of P. As a result, P developed several complications. Advise P as to against whom, that is, A or S, he should file the suit for damages.