Question

What is the total area of the interior faces of this composite solid?

The figure consists of 2 solid shapes that resemble bricks connected at one corner, forming a right angle there. One shape has a length of 8 meters, a width of 7 meters, and a height of 7 meters. The other shape has a length of 7 meters, a width of 8 meters, and a height of 7 meters. Filling the corner formed by the right angle is a three-sided figure whose vertex fits into the right angle. The base of this figure is straight and connects the other 2 vertices of the bricks, which are at the outside of the right angle.