9.85 The differential amplifier of Fig. 9.32(a) is measured and found to have a short-circuit transconductance of 2 mA/V. A differential input signal is applied and the output voltage is measured with a load resistance R L connected. It is found that when R L is reduced from ∞ to 20 k, the magnitude of the output signal is reduced by half. What do you estimate Ro and A d (with RL disconnected) to be?