The fixed money rent or the bighori, determined under section 151, of an occupancy, an exproprietary of a hereditary tenant shall be liable to abatement on one or more of the following grounds:--
         (a) that the rent payable by the tenant is substantially greater than the rent calculated at the sanctioned rates appropriate to him; or
         (b) that the productive power of the land held by the tenant has decreased by any cause beyond the control of the tenant during the currency of the present rent; or
         (c) in case of fixed money rent, that the area of his holding has been decreased by diluvion, or by the taking up of land for a public purpose, or for a work of public utility.