How to put multiple images into one figure in Latex

AKA, get four subfigures in one plot in Latex. easily:

After wasting an hour of my time, this is the answer:

\begin{figure}[htbp]
\begin{center}
\mbox{
{\bf a.}
\pdfimage width 3in {HLAarea2.png} \quad
{\bf b.}
\pdfimage width 3in {TEMPERATURE.png}
}
\mbox{
{\bf c.}
\pdfimage width 3in {magicplot_aug19_0830.jpg} \quad
{\bf d.}
\pdfimage width 3in {magicplot_aug19_1330.jpg}
}
\caption{Need better (a): (need better pic which indicates IW positions)}
\label{fig:1}
\end{center}
\end{figure}

The result (why does LaTeX and getting help with LaTeX have to be so difficult):