If the Ge diode in the circuit is reverse biased, the current through $2\mathrm{k\Omega }$ resistor

The $6 \mathrm{V}$ Zener diode shown in the figure has negligible resistance and a knee current of $5 \mathrm{mA}$. The minimum value of $\mathrm{R}\mathrm{ }\left(\mathrm{in}\mathrm{ }\mathrm{\Omega }\right)$ so that the voltage across it does not fall below $6 \mathrm{V}$ is

In a common emitter amplifier, the input resistance and output resistance are $200\mathrm{\Omega }$ and $500\mathrm{\Omega }$ respectively. If the voltage gain of the amplifier is $50$, then the power gain is

The following figure is the combination of logic gates, The inputs are $A$ are $B.$ The output is $C.$ Which one of the following choices gives the correct matching ?