Elements $X$ and $Y$ form two non-volatile compounds ($XY$ and $XY_3$). When $10 \ g$ of $XY$ is dissolved in $50 \ g$ of ethanol,the depression in freezing point $(\Delta T_{f})$ is $5.333 \ K$. When $10 \ g$ of $XY_3$ is dissolved in $50 \ g$ of ethanol,the $\Delta T_{f}$ is $2.2857 \ K$. What are the atomic weights of $X$ and $Y$ respectively? $(K_{f} = 2 \ K \ kg \ mol^{-1})$

• A
  $50 \ u, 50 \ u$
• B
  $25 \ u, 25 \ u$
• C
  $75 \ u, 100 \ u$
• D
  $25 \ u, 50 \ u$