Whether, with reference to the Minister of Mineral Resources’ reply to question 3396 on 14 November 2017, her department is aware of any salary scales used by the mining sector when it classifies paygrades; if not, what is the position in this regard; if so, what are the relevant details of the (a) salary band for each category and (b) number of persons employed as (i) permanent employees and (ii) outsourced contractors in the (aa) platinum group metals and (bb) gold sectors in each of the specified salary scales for each financial year since 1 April 2006?