\[\boxed{\mathbf{240.}}\]
\[p = 0,74;\ \ q = 0,26.\]
\[\textbf{а)}\ C_{3}^{0} + {0,74}^{0} + {0,26}^{3} =\]
\[= 1 \cdot 1 \cdot 0,017576 \approx 0,018.\]
\[\textbf{б)}\ C_{3}^{3} \cdot {0,74}^{3} \cdot {0,26}^{0} =\]
\[= 1 \cdot 0,405224 \cdot 1 \approx 0,405.\]