Research students from two classes A and B participate in a research camp. 
boys and 
girls from A class participate, and 
boys and 
girls from B class participates. They accidentally line up. Calculate the probabilities of the following events:
Students from the same class sit together,
girls stand together and boys stand together,
girls stand together,
B class girls stand together,
at the beginning and end of the line stands a boy,
girls stand in between between A class boys and B class boys.
