15. It shall be the duty of every police-officer-(a) promptly to serve every summons and obey and execute every warrant or other order lawfully issued to him by competent authority, and to endeavour by all lawful means to give effect to the lawful commands of his superiors;(b) to the best of his ability to obtain intelligence concerning the commission of cognizable offences or designs to commit such offences, and to lay such information and to take such other steps, consistent with law and the orders of his superiors, as are best calculated to bring offenders to justice or to prevent the commission of cognizable offences, or the commission of non-cognizable offences within his view;(c) to the best of his ability to prevent the commission of public nuisances; (d) to apprehend without unreasonable delay all persons whom he is legally authorised to apprehend and for whose apprehension there is sufficient reason;(e) to aid another police-officer, when called on by him or in case of need in the discharge of his duty, in such ways as would be lawful and reasonable on the part of the officer aided;(f) to discharge such duties as are imposed upon him by any law for the time being in force.