From the original pair of equations

The best extraction of terms to derive a minimal multi-level form is the following:

The final minimal implementation requires 11 gates and 13 literals.

Note: Some people attempted to draw K-maps of the two functions and minimize them as two-level implementations. In this case F is further simplified and it can be drawn with only 4 gates. However the idea of the problem wasn't to produce a two-level, but a multi-level minimization. That means that you were not supposed to remove any redundancy existing in the functions. Remember that sometimes redundancy is necessary, like in hazards.