The board shall order the boundaries of the district changed so as to include the land described in the inclusion petition, or such portion thereof as the board has found it feasible to serve by the system of works of the district and for the best interests of the district to include, only if:
(a) No protest against such change is made to the board in writing by the board, or a protest has been made and withdrawn.
(b) No protest against such change is made by holders of title to land pursuant to Section 48250, or such protest has been made and enough signatures withdrawn to render it insufficient.