In the process of movement water in the diffusion of water the net movement of water goes from higher concentration to the low concentration area. The movement of water move form one side to other side until it reaches an equilibrium and the level of water on the other side goes up.
Hence, the water molecule will move from from side B to side A until it reaches equilibrium and the water level on side A goes up.
0%?... i mean if 100 million years is half of its life then 300 million years surpasses its entire lifetime which would be 200 million years. Based off of this I don’t believe there’d be anything left