Re your question about Government Royalty on sales:I am not...

Re your question about Government Royalty on sales:

I am not aware of the % or basis, but 2017 Annual Report has GovtRoyalties as $4.596M and Revenue from Sale of Concentrates as $127.078M (notes 6 and 4 to the Financial Statement).

This ratio is 3.6% but of course there will be timing differences between the sales and royalty payments, so using 5% as Royalty rate for your calculation may be appropriate, but note that "revenue to the state" might also include other payments such as payroll tax, land taxes, GST etc etc