What Is the [H₃O⁺] in a Solution That Consists of 0.15

Multiple Choice

What is the [H₃O⁺] in a solution that consists of 0.15 M C₂N₂H₈(ethylene diamine) and 0.35 C₂N₂H₉Cl?
K_b = 4.7 $\times$ 10^-4

A) 2.0 $\times$ l0^-3 M
B) 1.1 $\times$ 10^-3 M
C) 6.3 $\times$ 10^-9 M
D) 2.1 $\times$ 10^-10 M
E) 5.0 $\times$ 10^-11 M