BC would equal the same as EF, they are similar. All you would have to do is figure out the pre image (BC) of EF.
The polyhedron has:
6 Faces, 8 vertices and 12 edges <u>in</u><u> </u><u>total</u><u>.</u>
But
3 Faces, 7 vertices and 7 edges <u>are</u><u> </u><u>visible</u><u>.</u>