\[\boxed{\mathbf{4.102}}\]
\[\textbf{а)}\ MN = 64\ м = 6400\ см;\ \ \]
\[MK = 6\ м\ 75\ см = 675\ см:\]
\[S_{\text{KNP}} = 6400 \cdot 675\ :2 =\]
\[= 3200 \cdot 675 = 2\ 160\ 000\ см^{2} =\]
\[= 216\ м^{2}.\]
\[\textbf{б)}\ MN = 9\ дм\ 5\ см = 95\ см;\ \ \]
\[MK = 15\ дм\ 8\ см = 158\ см:\]
\[S = 95 \cdot 158\ :2 = 95 \cdot 79 =\]
\[= 7505\ см^{2}.\]