V_V__ - R_S_ R_R_R_R_R_R_S_Rer_Re R_R_S_S_S_,r_R_ S_R_R_R_R_ S_R_S_R_R_ R_S_S_S_ R_Rer_S_S_ S_R_S_S_ R_S_ R_R_R_S_S_S_.r_R_R_ R_