Assume that the shape of Virginia beach is rectangular.
Note that
1 km = 10³ m
1 cm = 10⁻² m
The area is
A = (15 km)*(50 km)
= (15 x 10³ m)*(50 x 10³ m)
= 7.5 x 10⁸ m²
Because 2 cm of rain fell, the volume is
V = (7.5 x 10⁸ m)*(2 x 10⁻² m) = 1.5 x 10⁶ m³
Answer: 1.5 x 10⁶ m³