Ответ:

\[a \in \left( \frac{3}{8};\frac{3}{4} \right):\]
\[a = \frac{3}{8} \Longrightarrow A = \frac{8}{3} \cdot \frac{3}{8} = 1.\]
\[a = \frac{3}{4} \Longrightarrow A = \frac{8}{3} \cdot \frac{3}{4} = 2.\]
\[A \in (1;2).\]
\[Ответ:\ A \in (1;2).\]

\[a \in \left( \frac{3}{8};\frac{3}{4} \right):\]
\[a = \frac{3}{8} \Longrightarrow A = \frac{8}{3} \cdot \frac{3}{8} = 1.\]
\[a = \frac{3}{4} \Longrightarrow A = \frac{8}{3} \cdot \frac{3}{4} = 2.\]
\[A \in (1;2).\]
\[Ответ:\ A \in (1;2).\]