Find $[OH^{-}]$ if a monoacidic base is $3 \%$ ionised in its $0.04 \ M$ solution.

• A
  $3.1 \times 10^{-2} \ mol \ L^{-1}$
• B
  $4.5 \times 10^{-3} \ mol \ L^{-1}$
• C
  $9.0 \times 10^{-2} \ mol \ L^{-1}$
• D
  $1.2 \times 10^{-3} \ mol \ L^{-1}$