\[\boxed{\ \mathbf{501.}}\]
\[1)\ 48 \cdot 324 + 48 \cdot 276 =\]
\[= 48 \cdot (324 + 276) = 48 \cdot 600 =\]
\[= 28\ 800\]
\[2)\ 398 \cdot 81 - 81 \cdot 198 =\]
\[= 81 \cdot (398 - 198) = 81 \cdot 200 =\]
\[= 16\ 200\]