The Air Force originally planned to procure 165 of the B-2 bomber, but Congress reduced that to 21 aircraft.
7,377 Lancaster bombers were built.
At the height of the Luftwaffe's power they had about 2,800 bombers. Almost all of these were what the Allies would class as 'light bombers'.
two
21
There are many single engine aircraft used as dive bombers and torpedo bombers that could be cited if this were the aim of the question - was it?
3 u.s bombers disapeared during world war 2
No stealth bombers are on order. They already built all the Air Force could afford.
3
4
Approximately 100 were produced.
Many different engines are used in aircraft, including fighter bombers. You would need to name a specific aircraft to get the answer.
Many airplanes were used in WW1. The British had at least 12 kinds of fighters, 10 12 kinds of bombers and many 'observation aircraft. The Germans had many more kinds of fighters , but fewer bombers. The French had many fighters and a few different bombers. Altogether at least 85-100 different aircraft