
$$\halign{
\hfil$#$ & $= {#}\hfil$ \cr
m{\cal A} - {\cal B} + b{\cal X} & 0 \cr
m{\cal A} - {\cal B} + {{\cal Y} - m{\cal X}\over N}{\cal X} & 0 \cr
m{\cal A} - {\cal B} + {{\cal XY} - m{\cal X}^2\over N}      & 0 \cr
mN{\cal A} - N{\cal B} + {\cal XY} - m{\cal X}^2      & 0 \cr
m(N{\cal A} - {\cal X}^2 )     &  N{\cal B} - {\cal XY}  \cr
%m  & N{\cal B} - {\cal XY}  \over  N{\cal A} - {\cal X}^2 \cr
}$$