\[\boxed{\mathbf{115.}}\]
\[\textbf{а)};\ б)\]
\[\textbf{в)}\ P(A) =\]
\[= \frac{1}{2} \cdot \frac{1}{3} + \frac{1}{2} \cdot \frac{1}{2} \cdot \frac{1}{2} + \frac{1}{2} \cdot \frac{1}{2} =\]
\[= \frac{1}{6} + \frac{1}{8} + \frac{1}{4} = \frac{4 + 3 + 6}{24} = \frac{13}{24}.\]