In how many ways can a photographer at a wedding arrange 6 people in a row from a group of 10 people, where the bride and the groom are among these 10 people, if
a) the bride must be in the picture?
b) both the bride and groom must be in the picture?
c) exactly one of the bride and groom is in the picture?
I'm having trouble intuitively understanding how this works. Can someone explain to me what it means when the "bride must be in the picture, etc." and how this effects the number of arrangements?