The Base-Dissociation Constant of Ethylamine $\mathrm { C } _ { 2 }$

The base-dissociation constant of ethylamine ( $\mathrm { C } _ { 2 }$ $\mathrm { H } _ { 5 }$ $\mathrm { NH } _ { 2 }$ ) is 6.4 × $10 ^ { - 4 }$ at 25.0 °C.The [ $\mathrm { H } ^ { + }$ ] in a 1.7 × 10^-2 $\mathrm { mol } \mathrm { L } ^ { - 1 }$ solution of ethylamine is ________ mol L^-1.

A) 1.1 × 10^-5
B) 11.48
C) 3.3 × 10^-3
D) 3.0 × 10^-3
E) 3.3 × 10^-12