4.
\begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{3caa00c9-8a77-4987-888d-054eba7712ee-01_279_524_1078_1873}
\captionsetup{labelformat=empty}
\caption{Figure 1}
\end{figure}
Figure 1 shows a sketch of the curve with polar equation
$$r = a + 3 \cos \theta , \quad a > 0 , \quad 0 \leq \theta < 2 \pi .$$
The area enclosed by the curve is \(\frac { 107 } { 2 } \pi\).
Find the value of \(a\).