When an assessment is offered in a mahal in which both superior and inferior proprietors co-exist---a) if all the proprietors of the class with which the Settlement-officer proposes to make the settlement refuse to accept as aforesaid the assessment offered, the assessment shall be offered to the proprietors of the other class; and if all such proprietors refuse the assessment, the Settlement-officer shall proceed as provided in section fifty-seven;
         (b) if some only of the proprietors of the class with which the Settlement-officer proposes to make the settlement refuse the assessment, he may either proceed as if all had refused it or may deal with the mahal under section fifty-eight:
         Provided that if, in the case contemplated by clause (b), the proprietors who consented to accept the assessment when originally offered refuse to accept it, such assessment shall be offered to the other class of proprietors.