For a 0.0850 M solution of C6H5CH2COOH with a pH of 2.68, determine the value of Ka for C6H5CH2COOH.

a) 1.0 x 10⁻⁴
b) 2.0 x 10⁻⁴
c) 3.0 x 10⁻⁴
d) 4.0 x 10⁻⁴