Identify the correct output signal Y in the given combination of gates (as shown) for the given inputs A and B.

Two Zener diodes (A and B) having breakdown voltages of 6 V and 4 V respectively, are connected as shown in the circuit below. The output voltage V₀ variation with input voltage linearly increasing with time, is given by :
(V_input = 0 V at t = 0)
(figures are qualitative)

With increasing biasing voltage of a photodiode, the photocurrent magnitude :

Identify the operation performed by the circuit given below :