Stop in for a cup of coffee

Math word problem...

George is driving a bus that can carry 80 passengers and has made 3 stops already

At the next stop, 40% of the passengers get off the bus and 50% get on.

At the following stop, 18% get off and 36% get on.

At the last stop 70% get off and none get on.

Solve: What kind of sandwich does George have in his lunch box?