#### Answer

$T=82$ square km.

#### Work Step by Step

The area of this figure can be calculated as the sum of the area of the rectangle and the area of the trapezoid on the top.
$T=T_1+T_2$
Rectangle:
$T_1=a\times b$
$T_1=10\times5=50$ square km.
Trapezoid:
$T_2=h\times \frac{a+c}{2}=4\times \frac{6+10}{2}=4\times 8=32$ square km
$T=T_1+T_2=50+32=82$ square km.