The $K_a$ of $CH_3COOH$ is $1.76 \times 10^{-5}$ at $298 \ K$. Calculate the dissociation constant $(K_b)$ of its conjugate base.

• A
  $5.68 \times 10^{-10}$
• B
  $5.90 \times 10^{-10}$
• C
  $1.76 \times 10^{-9}$
• D
  $1.00 \times 10^{-14}$