(1) The attributable part of the land value of land described in section 585(a) or (b) is determined by deducting from the land value the value that the land would have if the land could be used only as the site of a single dwelling-house.
(2) The attributable part of the land value of land described in section 585(c) that may be used otherwise than as rural land is determined by deducting from the land value the value that the land would have if the land could be used only as rural land.
(3) The attributable part of the land value of land described in section 585(c) that may be subdivided into one or more lots having an area of less than 40 hectares is determined by deducting from the land value the value that the land would have if the land could only be subdivided into lots having an area of 40 hectares or more.