9.61 The differential amplifier circuit of Fig. P9.61 utilizes a resistor connected to the negative power supply to establish the bias current I. (a) For vB1 = vid/2 and vB2 =−vid/2, where vid is a small signal with zero average, find the magnitude of the differential gain, vo/vid . (b) For vB1 = vB2 = vicm, where vicm has a zero average, find the magnitude of the common-mode gain, vo/vicm . (c) Calculate the CMRR. (d) If vB1 =0.1 sin 2π × 60t + 0.005 sin 2π × 1000t, volts, and v B2 =0.1 sin 2π ×60t −0.005 sin 2π ×1000t, volts, find v o.