pH of acid or base mixtures

Exercise 1

Determine the $pH$ of the solution obtained by mixing $V_1$ = 350 $mL$ $HClO_4$ 0.95 $M$ with $V_2$ = 50 $mL$ $HCl$ 0.65 $M$

$HClO_4$ ,$ HCl$ :    strong acids $n_{HClO_4}$ $=$ $c_{HClO_4}\cdot V_1$ = 0.3325 $mol$ $n_{HCl}$ $=$ $c_{HCl}\cdot V_2$ = 0.0325 $mol$ $pH$ $=$ $-log\frac{n_{HClO_4} + n_{HCl}}{V_1+V_2}$ = 0.04