(1)If, under any of the following provisions of this Chapter, this Chapter applies to part only of the capital expenditure on plant and machinery—
(a)the part to which this Chapter applies, and
(b)the part to which it does not,
are to be treated for the purposes of this Act as expenditure on separate items of plant or machinery.
(2)For the purposes of subsection (1), all such apportionments are to be made as are just and reasonable.