Answer: 410 square km
Step-by-step explanation:
The area of each of the triangles with their base on the 10 km side is , so their combined area is
.
The area of each of the triangles with their base on the 12 km side is , so their combined area is
.
The area of the bottom rectangular face is .
So, the total surface area is
BC = JC by the single tickmarks shown
CD = CD because of the reflexive property
The angles between these two pairs of sides, that you've marked in the second answer choice, are needed to use SAS (side angle side).
See the diagram below. In the diagram, angle BCD (green) is between segments BC and CD. Also, angle JCD (blue) is between JC and CD.
