The situation: A 5' wide corridor. At the end of the hallway is a medium humanoid. In front of him is a medium PC, engaged in melee combat with the humanoid. 30' back down the hallway is the PC's friend, a PC archer. The archer wants to shoot at the humanoid. It's -4 to hit because his target is engaged in melee. Does the humanoid ALSO get cover (+4 AC) because the archer's friend is in the way?