(2)The expenditure referred to in sub-section (1) is the expenditure incurred by the assessee at any time during the year of commercial production and any one or more of the four tax years immediately preceding that year, wholly and exclusively on any operations relating to prospecting for any mineral or group of associated minerals specified in Part A or Part B, respectively, of the Schedule XII or on the development of a mine or other natural deposit of any such mineral or group of associated minerals.
