\[\boxed{\mathbf{353}\mathbf{.}}\]
\[1)\ 28 \cdot \frac{1}{2} = 14\]
\[2)\ 28 \cdot \frac{3}{7} = 4 \cdot 3 = 12\]
\[3)\ 28 \cdot \frac{9}{14} = 2 \cdot 9 = 18\]
\[4)\ 28 \cdot \frac{19}{28} = 1 \cdot 19 = 19\]