Eight chairs are arranged in two equal rows for a group of $8$. Joe and Mary must sit in the front row. Jack must sit in the back row. How many different seating plans can they have?

Two Britons, three Americans, and six Chinese form a line:

• How many different ways can the $11$ individuals line up?
• If two people of the same nationality cannot stand next to each other, how many different ways can the $11$ individuals line up?