The input-load resistor is 150K-Ohms. Using the standard hi-pass-filter formula of F = 159155/RC, where F = Filter (-3dB) Point in Hz, R = resistance in Ohms, and C = capacitance in microFarads, the existing calculation is F = 159155/(0.01*150,000), = 106Hz.
Plug any values for C you want in the formula and Bingo! you have a new number.