Two point sources, 5.0 cm apart, are operating in phase, with a common frequency of 6.0 Hz, in a ripple tank. A metre stick is placed above the water, parallel to the line joining the sources. The first nodal lines (the ones adjacent to the central axis) cross the metre stick at the 35.0-cm and 55.0-cm marks. Each of the crossing points is 50.0 cm from the midpoint of the line joining the two sources. Draw a diagram of the tank, and then calculate the wavelength and speed of the waves.