If a fee or allowance is discretionary, the taxing officer is to take into consideration the following:(a) any other fee or allowance in respect of the work to which the fee or allowance relates;(b) the nature and importance of, and the amount involved in, the proceedings;(c) the interest of the parties;(d) the person, estate or fund by whom or by which the costs are to be borne;(e) the general conduct and costs of the proceedings;(f) any other relevant circumstances.