I think the answer would be 5162 because
First we would need to find the volume of the cube.
To find volume we do 21x18x13 and get 4914
Next we need to find the area of the two triangles. So to find the area of the triangle we do 16 times half of 18 so 16x9= 72 (we also have to divide 72 by two but we won’t because there is two triangles, to find area of one triangle divide 72 by 2 but we have two triangles.)
Next we do the other triangle on the right side. So 16 x (.5 x13)= 104 (104 is the total for two triangles)
Now we add all of our areas together and get 4914
