Among `PbS,CuS,HgS,Ag_(2)S,NiS,CoS,Bi_(2)S_(3)` and `SnS_(2)` the total no of BLACK coloured sulphides is

Among PbS, CuS, MnS, Ag_(2)S, NiS, CoS, Bi_(2)S_(3) and SnS_(2) the total number of block coloured sulphides is

Consider the sulphides HgS, PbS, CuS, Sb_(2)S_(3), As_(2)S_(3) and CdS. Number of these sulphides soluble in 50% HNO_(3) is__________

The K_(sp) of CuS, Ag_(2)S and HgS are 10^(-31), 10^(-44) and 10^(-54) respectively. The solubility of these sulphides are in the order.