Amplifier A has an input resistance of 1M Ω, an output resistance of 200Ω, and an open-circuit trans-resistance gain of 100MΩ. Amplifier B has an input resistance of 50Ω, an output impedance of 500 k Ω, and a short circuit current gain of 100. Find the voltage amplifier model for the cascade of A followed by B. Then, determine the corresponding trans-conductance amplifier model.