The following two waves are sent in opposite directions on a horizontal string so as to create a standing wave in a vertical plane: y1(x, t) = (6.00 mm) sin (4.00px - 400pt) y2 (x, t) = (6.00 mm) sin (4.00px + 400pt), with x in meters and t in seconds. An anti node is located at point A. In the time interval that point takes to move from maximum upward displacement to maximum downward displacement, how far does each wave move along the string?