$24.8\mathrm{kg}$ of pure argentite, $\mathrm{Ag}{}_2\mathrm{S}$ (molar mass 248), is leached by $\mathrm{Ag}{}_2\mathrm{S}+4\mathrm{NaCN}\to 2\mathrm{Na}[\mathrm{Ag}(\mathrm{CN}){}_2]+\mathrm{Na}{}_2\mathrm{S}$. Air oxidises the sulphide formed by $2\mathrm{Na}{}_2\mathrm{S}+2\mathrm{O}{}_2+\mathrm{H}{}_2\mathrm{O}\to \mathrm{Na}{}_2\mathrm{S}{}_2\mathrm{O}{}_3+2\mathrm{NaOH}$, and silver is recovered by $2\mathrm{Na}[\mathrm{Ag}(\mathrm{CN}){}_2]+\mathrm{Zn}\to \mathrm{Na}{}_2[\mathrm{Zn}(\mathrm{CN}){}_4]+2\mathrm{Ag}$. With $\mathrm{NaCN}=49$, $\mathrm{O}{}_2=32$, $\mathrm{Zn}=65$, the masses of NaCN, $\mathrm{O}{}_2$ and Zn dust required (stoichiometric, complete reactions) are respectively

1. A9.8 kg, 3.2 kg, 6.5 kg
2. B19.6 kg, 3.2 kg, 6.5 kg
3. C19.6 kg, 1.6 kg, 6.5 kg
4. D19.6 kg, 3.2 kg, 13.0 kg