What Is the Equilibrium Hydronium Ion Concentration of an Initially $2.3 \times 10 ^ { - 11 }$

What is the equilibrium hydronium ion concentration of an initially 4.5 M solution of hypoiodous acid, HOI, at 25°C (K_a = $2.3 \times 10 ^ { - 11 }$ ) ?

A) $1 \times 10 ^ { - 5 }$ M
B) $1 \times 10 ^ { - 7 }$ M
C) $7.2 \times 10 ^{- 6}$ M
D) $1.4 \times 10 ^ { - 5 }$ M
E) $2.26 \times 10 ^{- 6}$ M