The following input-output pairs have been observed during the operation of a linear system: x1(n) = f−1; 2; 1g ! t y1(n) = f1; 2; −1; 0; 1g x2(n) = f1; −1; −1g ! t y2(n) = f−1; 1; 0; 2g x3(n) = f0; 1; 1g ! t y3(n) = f1; 2; 1g a) suppose the input signal is x(n) = (n), what is the resulting output signal? b) determine whether the system is time-invariant. justify your answer.