JEE Main 2023 Chemistry question on Equilibrium

A litre of buffer solution contains 0.1 mole of each of $\text{NH}_3$ and $\text{NH}_4\text{Cl}$. On the addition of 0.02 mole of HCl by dissolving gaseous HCl, the pH of the solution is found to be __________ $\times 10^{-3}$ (Nearest integer)

[Given : $\text{pK}_b(\text{NH}_3) = 4.745$
$\log 2 = 0.301$
$\log 3 = 0.477$
$T = 298 \text{ K}$]