What is the pH change observed on adding 0.010 mol HCl to 1.00L of 0.10 M C6H5CO2H (Ka=6.5 X 10^-5)?

I'm not sure how to find the final pH.What is the pH change observed on adding 0.010 mol HCl to 1.00L of 0.10 M C6H5CO2H (Ka=6.5 X 10^-5)?
1.

[H+] = square root (Ka*Ca) = 2.55*10^-3 M

pH = 2.59



2.

pH = - log Ca = 2.00



螖pH = 2.00 - 2.59 = - 0.59