399.6. For the purposes of this chapter, the expression “restricted expense” of a taxpayer means an expense(a) incurred by him before 1 April 1987;
(b) that is deemed under section 418 to have been incurred by him, or included by him in the amount referred to in paragraph a of section 408 by virtue of the second paragraph of section 392, to the extent that the expense was originally incurred before 1 April 1987;
(c) that was renounced by him under section 359.2.1 or 359.4 or section 417, as it read in respect of the renunciation;
(d) in respect of which an amount referred to in section 392 becomes receivable by him;
(e) deemed to be a Canadian exploration expense of the taxpayer or any other taxpayer by virtue of section 399.3; or
(f) where the taxpayer is a corporation, that was incurred by the corporation before the time control of the corporation was last acquired by a person or persons.