When 01 Mole of Methylamine Is Dissolved in 500 ML of of Water

When 0.1 mole of methylamine is dissolved in 500 mL of water, the following hydrolysis reaction occurs:
H₂O_(l) + CH₃NH_2(aq) CH₃NH₃⁺_(aq) + OH^-_(aq)
The hydroxide concentration is found to be 8.6 x10^-3 M when equilibrium is reached. What is the value of the equilibrium constant for this reaction?

A) 4.3 x 10^-2
B) 7.4 x10^-4
C) 7.4 x 10^-5
D) 3.9 x 10^-4
E) 7.4 x 10^-3