\textbf{103-} The figure shows part of the graph of $y = a\sin\pi\!\left(\dfrac{1}{2} + bx\right)$. What is $a \cdot b$?
\textit{[Figure: Graph of a sinusoidal function with amplitude $2$, showing values at $x = 3.5$ and minimum $-2$, with dashed line at $y=2$]}
\begin{itemize}
\item[(1)] $2$
\item[(2)] $2.5$
\item[(3)] $3$
\item[(4)] $3.5$
\end{itemize}