In the circuit shown below, the op-amp is ideal and Zener voltage of the diode is 2.5 volts

Q. 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(𝑡) = 𝑢(𝑡) 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

(A) 2.5               (B) 5   (C)   7.5               (D) 10

Ans: 7.5