Point B is at the trough, point A is at the peak, and the wave propagates from B to A. At this time, C is in an equilibrium position. After a quarter period, the trough propagates to this point, which shows that the vibration direction of point C is downward.

The period t = λ V = 0.2 1s = 0.2s, and the distance that a particle vibrates in a period is equal to 4 times the amplitude. When it passes 0.25 seconds, the moving distance is equal to 5 times of the amplitude. A = 20cm, then S =100cm.

So the answer is: down, 100.