Assuming both the voltage sources are in phase, the value of R for which maximum power is transferred from circuit A to circuit B is

For the circuit given above, the Thevenin's resistance across the terminals $$A$$ and $$B$$ is

For the circuit given above, the Thevenin's voltage across the terminals $$A$$ and $$B$$ is

In the given Fig. the Thevenin's equivalent pair (voltage, impedence), as seen at the terminals $$P-Q$$, is given by