By definition, the area of a rectangle can be calculated using the following formula:
[tex]A=lw[/tex]Where "l" is the length and "w" is the width of the rectangle.
In this case you know that:
[tex]\begin{gathered} l=6.5\operatorname{km} \\ w=3.4\operatorname{km} \end{gathered}[/tex]Therefore, knowing the length and the width of this rectangle, you can susbstitute them into the formula for calculate the area of a rectangle:
[tex]\begin{gathered} A=(6.5\operatorname{km})(3.4\operatorname{km}) \\ A=22.1\operatorname{km}^2 \end{gathered}[/tex]The answer is:
[tex]A=22.1\operatorname{km}^2[/tex]