A trustee may be discharged from his office only as follows:--
     (a) by the extinction of the trust;
     (b) by the completion of his duties under the trust;
     (c) by such means as may be prescribed by the instrument of trust;
     (d) by appointment under this Act of a new trustee in his place;
     (e) by consent of himself and the beneficiary, or, where there are more beneficiaries than one, all the beneficiaries being competent to contract; or
     (f) by the Court to which a petition for his discharge is presented under this Act.