Rate of reaction for $2X + Y \rightarrow 3W + Z$ is $1.2 \times 10^{-4} \ mol \ dm^{-3} \ sec^{-1}$ when $[X] = [Y] = 0.6 \ mol \ dm^{-3}$. Calculate the value of the rate constant if the reaction is first order in $X$ and zero order in $Y$.

• A
  $2 \times 10^{-4} \ sec^{-1}$
• B
  $6 \times 10^{-3} \ mol \ dm^{-3} \ sec^{-1}$
• C
  $4 \times 10^{-4} \ sec^{-1}$
• D
  $1.8 \times 10^{-3} \ mol \ dm^{-3} \ sec^{-1}$