\[\boxed{\mathbf{140.}}\]
\[\textbf{а)}\ 4 \cdot 8 \cdot 5 = 4 \cdot 40 = 160\]
\[\textbf{б)}\ 7 \cdot 4 \cdot 9 = 63 \cdot 4 = 252\]
\[\textbf{в)}\ 5 \cdot 13 \cdot 21 = 65 \cdot 21 = 1365\]
\[\textbf{г)}\ 8 \cdot 7 \cdot 6 = 56 \cdot 6 = 336\]