I was posted an interesting situation from one of the players in my game. He stated that he noticed since he is a Tabaxi\Monk and once he levels up 5 times in Monk Magic to get the Longstrider Ability and boosts of speed ability then adds his racial speed boost and then someone casts haste on him, this would give him a movement of 3000' for movement. I know you can't stack certain speed boosts.
My question is: do any of these stack? If so, which ones and what would his speed become in that scenario?