\[\boxed{\mathbf{272.}}\]
\[\textbf{а)}\ DX = 13\ 500 \cdot \frac{1}{3} \cdot \frac{2}{3} =\]
\[= 1500 \cdot 2 = 3000.\]
\[\textbf{б)}\ DX = 13\ 500 \cdot \frac{1}{6} \cdot \frac{5}{6} =\]
\[= 375 \cdot 5 = 1875.\]