[填空题]
Let f(x)=p $\sin (q x)+r$ , for $x \in \mathbb{R} $.
Part of the graph of f is shown on the diagram below.
The graph of f has a minimum at $\mathrm{A}(3,-1)$ and a maximum at $\mathrm{B}(9,5)$ .
1. 1. Find the period of f .
2. Hence find the value of q .
2. Find the values of:
1. p ;
2. r .
3. Solve f(x)=4 , for 0 $\leq x \leq 15$ .
