A math problem

The answer is 7. The process that students say is a bit complicated, and the relatively simple process is as follows (note: lowercase letters all mean vectors, so I can't type them out):

The original formula =èA * A-A * B+B * A-B * Bè, and because vector A is perpendicular to vector B, the dot products of their points are all zero vectors, so the original formula =èA * A-B * Bè=èAè.

You said I miscalculated. I want to ask, is the multiplication symbol in your middle a pointer product or a cross product? If it's dot product, it's right. If it is a cross product, the answer is 24.