8 people are lining up in a row for a photograph. 1) how many different line ups are there? 8! 2) how many different line ups are there if a and b do not stand next to each other? 3) how many different line ups are there if a is not in the leftmost position? 4) how many different line ups are there if b is not at the end? (i.e., in the leftmost or the right most position)