(1) What is the breakdown of the taxable income derived from the mining sector in terms of each of the specified top 20 mining companies in the (a) 2013-14 and (b) 2014-15 financial years; (2) what is the effective tax rate for each of the specified top 20 mining companies, with particular reference to (a) BHP Billiton Ltd and (b) EXXARO Resources?