With reference to the total amount that was paid to each (a) deep water mining, (b) tailings mineral resource reprocessing and (c) bedrock sweeping contractor by Alexkor in each of the past five financial years, what (i) is the total volume of gravels that were treated, (ii) carats of diamond were produced, (iii) is the total number of diamonds that were produced and (iv) is the total income that was generated?