How many grams of solid potassium fluoride should be added to 0.500 L of a 0.144 M hydrofluoric acid solution to prepare a buffer with a pH of 4.130? The Ka of hydrofluoric acid is 7.20×10⁻⁴.

a) 18.2 g
b) 22.5 g
c) 30.1 g
d) 40.8 g