A water wave demonstration tank is 40 m long. At one end, at the origin, Mary is generating waves described by the function y1=2.0 cm cos[/(9m) (4x-(8m/s)t]. At the other end Paul is generating waves described by y2=-3.0cm sin [2/(3s)((1s/m)x+2t)]. At x=10m, Peter is recording the water level.