(1) Subject to subsections (2) and (3), where a person carrying on the trade of working a qualifying mine incurs on or after the 6th day of April, 1974, any development expenditure or exploration expenditure and makes application under section 670 for a mine development allowance for a chargeable period in respect of such expenditure -
(a) that expenditure shall be deemed to be expenditure in respect of which that allowance may be granted, whether or not in the case of exploration expenditure a deposit of scheduled minerals is found as a result of the expenditure,
(b) the amount of such allowance for that chargeable period shall be equal to the total amount of -
(i) the exploration expenditure, and
(ii) in the case of development expenditure, the amount of the difference between that expenditure and the amount which in the opinion of the inspector the assets representing that expenditure are likely to be worth at the end of the estimated life of the qualifying mine, and
(c) in relation
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