Armand is monitoring a large sealed tank by way of a sensor that records the liquid level over time on a graph. He looks at the graph and claims that the sensor indicates there are waves in the liquid in the tank. Part A: Explain how Armand knows that there is a wave in the tank.

Part B: Find the amplitude, in centimeters (cm), and frequency, in number of waves every second/cycle per second (Hz), of the wave.