(1) In this section, "open-market price", in relation to any machinery or plant, means the price which the machinery or plant would have fetched if sold in the open market at the time of the event in question.
(2) Where -
(a) an event occurs which gives rise or might give rise to a balancing allowance or balancing charge in respect of machinery or plant,
(b) the event is the permanent discontinuance of a trade, and
(c) at or about the time of the discontinuance there occurs in relation to the machinery or plant any event mentioned in paragraphs (a) to (c) of section 318, not being a sale at less than open-market price other than a sale to which section 312 applies,
then, for the purpose of determining -
(i) whether the discontinuance gives rise to a balancing allowance or balancing charge, and, if so,
(ii) the amount of the allowance or, as the case may be, the amount on which the charge is to be made,
the amount of the net proceeds, compensation, receipts or insurance moneys mentioned
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