18. Where several persons holding decrees to which this Act applies move the court, before it has granted a mortgage-under section 17, for execution of their decrees by grant of a mortgage of land protected under that section, the court shall, subject to the provisions of that section, observe the following principles in executing the decrees.
(a) If any such decree is based on a loan the payment of which is already secured by a mortgage of the whole or part of the land so protected (hereinafter described as a secured decree) the holder of such decree shall first be granted a mortgage of the protected land already mortgaged to him, and the holder of a decree based on an unsecured loan (hereinafter described as an unsecured decree) shall be granted a mortgage of the remaining protected land, if any.
(b) Where there are more than one secured decrees and also unsecured decrees-
(i) and different portions of the protected land are mortgaged in the secured decrees, the holder of each such decree shall be granted a mortgage of the portion which is already mortgaged to him ;
(ii) and the same protected land is mortgaged in more than one decree, mortgages shall be granted to the holders of such decrees in order of their priority ;
(iii) and if after grant of mortgages under sub-clause (i) and (ii) there remains any protected land free from such mortgages, the holders of the unsecured decrees shall be granted mortgaged thereof.
(c) As among persons holding unsecured decrees, such persons shall each be granted simultaneously mortgages of ratable shares of the land in such manner as may be prescribed.