Balance this equation pls

__NaCl + __CaF2→ __NaF +__CaCl2

To extract gold from its ore, the ore is treated with sodium cyanide solution in the presence of oxygen and water. the balanced equation is:
4 au(s) + 8 nacn(aq) + o2(g) + 2 h2o(l) 4 naau(cn)2(aq) + 4 naoh(aq) 
use the equation to find out the mass of gold, using simple ratio method.