If $0.050\;mL$ of $0.6\;M\;HCl$ is added to 400 mL of $10^{-5}\;M\;HCl$ what is the resulting pH?

Question

$\begin{array}{1 1} (a)\;3.12 \\(b)\;7.12 \\ (c)\;8.12 \\(d)\;3.12 \end{array} $