$$\left. \begin{array} { l } { A - B + D = 3 \quad A - B - D = 1 } \\ { a + b + C = 0 } \\ { a + b + a = 3 } \\ { a + b - c = 0 } \\ { a - b - d = 1 } \end{array} \right.$$
$A=D$
$B\in \mathrm{C}$
$D\in \mathrm{C}$
$A=D$
$B\in \mathrm{R}$
$D\in \mathrm{R}$
