Given the amount of sample: 24.25 mL;
the concentration of the titrant (NaOH) = 0.1010 mol / L NaOH
the amount of the titrant used for titration = 14.83 mL
The concentration of a solution of lactic acid is determined by:
C(lactic acid in the sample) = ((0.1010 mol / L) * (14.83mL/1000) / (24.25mL/1000)
C = 0.0618 mol