In the circuit shown below, the op-amp is ideal and Zener voltage of the diode is $2.5\: volts$. At the input, unit step voltage is applied, i.e. $v_{IN}\left ( t \right ) = u\left ( t \right )\:volts$. Also, at $t = 0$, the voltage across each of the capacitors is zero.
The time $t$, in milliseconds, at which the output voltage $v_{OUT}$ crosses $-10\: V$ is
- $2.5$
- $5$
- $7.5$
- $10$
