If the quadrilateral formed by the lines `a x+b y+c=0,a^(prime)x+b^(prime)y+c=0,a x+b y+c^(prime)=0,a^(prime)x+b^(prime)y+c^(prime)=0` has perpendicular diagonals, then (a) `b^2+c^2=b^('2)+c^('2)` (b)`c^2+a^2=c^('2)+a^('2)` (c)`a^2+b^2=a^('2)+b^('2)` (d) none of these