4 The numbers of rides taken by two students, Fei and Graeme, at a fairground are shown in the following table.
- The mean cost of Fei's rides is \(
) 2.50\( and the standard deviation of the costs of Fei's rides is \)\\( 0\). Explain how you can tell that the roller coaster and the water slide each cost \(
) 2.50\( per ride. [2] - The mean cost of Graeme's rides is \)\\( 3.76\). Find the standard deviation of the costs of Graeme's rides.