Formic Acid, HCO₂H, Has an Ionization Constant with the Value

Formic acid, HCO₂H, has an ionization constant with the value: K_a = 1.76 × 10^?4. Calculate the value of pK_b for the formate ion, CO₂H^-, the conjugate base of formic acid.

A) 3.75
B) 5.35
C) 8.65
D) 10.25
E) 12.24