To find the total area of Oak Manor, you can use the formula for the area of a rectangle:
\[ \text{Area} = \text{Length} \times \text{Width} \]
In this case, the length is 4.2 miles and the width is 3.8 miles:
\[ \text{Area} = 4.2 , \text{mi} \times 3.8 , \text{mi} = 15.96 , \text{mi}^2 \]
Thus, the total area of Oak Manor is 15.96 mi².