What volume (in mL) of 1.0 M HCl is required to prepare 500 mL of pH 7.76 buffer using triethanolamine that is 0.020 M in both triethanolamine and triethanolammonium ion?

I found pKa for the base to be 7.76; therefore,

= 7.76 + log (0.02/0.02) so the pH of this solutiion is 7.76 and no HCl needs to be added/