The relationship connecting maximum rainfall $P_0$, average rainfall depth $P$, and area $A$ (in km\textsuperscript{2}) is:
\[P = P_0 \exp(-K A^n)\]
In this equation:
$P_0$ represents the maximum rainfall (cm),
$P$ denotes the average rainfall depth (cm),
$A$ is the region's area (km\textsuperscript{2}),
$K$ and $n$ are storm constants, which vary with storm characteristics.
The correct formula is $P = P_0 \exp(-K A^n)$ (Option 1).