2. A first-order hold performs, for nTs St≤ (n + 1)Ts, a linear extrapolation from the values at (n - 1)T, and nTs. (a) Write the analytic expression in the time domain for the extrapolated wave- forms. (b) Calculate the response to a discrete-time impulse [n]. (c) From (b), calculate the transfer function and plot its magnitude and pahse. Compare with the magnitude and phase of the zero-order hold.