what is the equilibrium constantKfinalfor the following reaction

Given the two reactionsH2S⇌HS−+H+,K1= 9. 72×10−8, andHS−⇌S2−+H+,K2= 1. 34×10−19,what is the equilibrium constantKfinalfor the following reaction?S2−+2H+⇌H2SGiven the two reactionsPbCl2⇌Pb2++2Cl−,K3= 1. 78×10−10, andAgCl⇌Ag++Cl−,K4= 1. 20×10−4,what is the equilibrium constantKfinalfor the following reaction?PbCl2+2Ag+⇌2AgCl+Pb2+