Section 58 of the Act of 1891 is hereby amended by the insertion of the following subsection after subsection (1):
"(1A) Where -
(a) any property which consists partly of an interest in residential property is sold to any person and the sale (hereinafter in this subsection referred to as ‘the first-mentioned sale’) does not form part of a larger transaction or of a series of transactions, or
(b) the sale to any person of property consisting in whole or in part of such an interest forms part of a larger transaction or of a series of transactions,
the consideration attributable to the first-mentioned sale and the aggregate consideration (other than rent) attributable to that larger transaction or series of transactions, as the case may be, shall be apportioned, on such basis as is just and reasonable, as between that interest in residential property and the other property or part concerned, and that aggregate consideration shall likewise be apportioned as between each other such