$\begin{array}{1 1}(a)\;21x+77y-93=0,99x-77y+63=0\\(b)\;20x+77y-90=0,99x-77y+60=0\\(c)\;21x-77y+93=0,99x+77y+63=0\\(d)\;2x+70y-93=0,99x-70y+63=0\end{array}$