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.
