The input signal $${V_{in}}$$ shown in the figure is a $$1$$ $$kHz$$ square wave voltage that alternates between $$+7V$$ and $$-7V$$ with a $$50\% $$ duty cycle. Both transistors have the same current gain, which is large. The circuit delivers power to the load resistor $${R_L}.$$ What is the efficiency of this circuit for the given input? Choose the closest answer.

$$IC$$ $$555$$ in the adjacent figure is configured as an Astable multivibrator. It is enabled to oscillator at $$t=0$$ by applying a high input to pin $$4.$$ The pin description is $$1$$ and $$8$$ $$-$$supply; $$2-$$trigger; $$4-$$reset; $$6$$-threshold; $$7$$-discharge. The wave form appearing across the capacitor starting from $$t=0$$ as observed on the storage $$CRO$$ is

The system shown in figure below
can be reduced to the form
With

If the loop gain $$K$$ of a negative feedback system having a loop transfer function $$K\left( {s + 3} \right)/{\left( {s + 8} \right)^2}$$ is to be adjusted to induce a sustained oscillation then