!$ V_S = - { \large R_o \over R} ( V_D + { \large V_c \over 2} + { \large V_B \over 4} + { \large V_A \over 8}) !$

!$ V_s = - { \large R_o \over R} ( { \large V_A \over R} + { \large V_B \over 2R} + { \large V_C \over 4R} + { \large V_D \over 8R}) !$

!$ V_s = - { \large R_o \over R} ( V_A + { \large V_B \over 2} + { \large V_C \over 4} + { \large V_D \over 8}) !$

!$ V_s = - { \large R_o \over R} ( { \large V_D \over R} + { \large V_C \over 2R} + { \large V_B \over 4R} + { \large V_A \over 8R}) !$