The graph below shows the displacement of a wave over time.

Use the graph to work out the time period of the wave.
Use the graph to work out the amplitude of the wave.
What is meant by the term frequency of a wave?
A sound wave has a frequency of 250 Hz250\text{ Hz}250 Hz and a wavelength of 1.36 m1.36\text{ m}1.36 m.
Calculate the speed of this wave.