Bestimmen Sie mittels Gauß-Elimination und Rickwärtseinsetzen die Lösungsmenge, bei c) in Abhängigkeit von den Parametern \( A, B \in \mathbb{R} \) (Fallunterscheidungen):
a)\[\left(\begin{array}{llll|l}{0} & {1} & {4} & {0} & {14} \\{6} & {0} & {0} & {1} & {10} \\{2} & {5} & {0} & {0} & {12} \\{0} & {0} & {0} & {3} & {12}\end{array}\right)\]b)\[\begin{array}{c}{\left(\begin{array}{lll|l}{6} & {7} & {8} & {4} \\{3} & {4} & {5} & {4} \\{0} & {1} & {2} & {1}\end{array}\right)} \\c){\left(\begin{array}{cccc|c}{1} & {3} & {2} & {1} & {2} \\{0} & {6} & {3} & {2} & {2} \\{-2} & {0} & {-1} & {0} & {B} \\{-3} & {3} & {0} & {A} & {0}\end{array}\right)}\end{array}\]