For all these number you have a big excess of HClO4. Do stoichiometry, calculate an excess of HCLO4 in a fonal volume, and calculate pH of an excess of a strong acid
For 260.9 ml and b - 114.1 mL and c - over 114,1 mL
you have problem
a) an excess of NaOH
b) equivalent point
c) excess of HClO4