Solve the following problem:
For the system of Fig. (a), the no-load output voltage is 1440 mV, with 1.2 mV applied at the input terminals.
In Fig. (b), a 4.7-kΩ load is applied to the same system, and the output voltage drops to 192 mV, with the same applied input signal. What is the output impedance of the system?
