A bicycle with a stone stuck in the tread of one of its tires is pushed along the street. The function graphed below models the height, in inches, of the stone above the ground after x seconds.

4. A bicycle with a stone stuck in the tread of one of its tires is pushed along the street. The function graphed below models the height, in inches, of the stone above the ground after x seconds. 0 I 2 a a s o 1 s 9 1o 11 I: .r a) Find an sine or cosine equation to model the graph. (2 marks) b) What is the diameter of the bicycle tire? (1 mark) c) How often does the stone hit the ground? (1 mark)