The Base- Dissociation Constant, K_b, for Pyridine, C₅H₅N, Is 1

The base- dissociation constant, K_b, for pyridine, C₅H₅N, is 1.4 × 10^{- 9}. The acid- dissociation constant, K_a, for the pyridinium ion, C₅H₅NH⁺, is _ .

A) 1.4 × 10^{- 5}
B) 7.1 × 10^{- 4}
C) 1.4 × 10^{- 23}
D) 7.1 × 10^{- 6}
E) 1.0 × 10^{- 7}