$[$Use Gy$\text{'}$s method to solve$]$

Regular samples were required of the feed to a copper processing plant, having a copper content of about $9\%.$ The confidence level of estimation was required to be $0\mathrm{.}1\%$ Cu at $2\backslash$sigma standard deviation. The liberation size of the Cu mineral $($chalcocite$)$ in the ore was determined to be $75\backslash$mu m$.$ A sieve analysis showed that the $95\%$ pass size and $5\%$ passing size were $2\mathrm{.}5$ cm and $50\backslash$mu m respectively. Determine the minimum mass of sample required to represent the ore. Given; the density of chalcocite is $5600$ kg$/$m$3$ and the density of the gangue is $2500$ kg$/$m$3.$