G2.2 Let $f(x)=p x^{7}+q x^{3}+r x-5$, where $p, q$ and $r$ are real numbers. If $f(-6)=3$ and $z=f(6)$ Find the value of $z$. (Reference: $\mathbf{1 9 9 5}$ FI1.3)
$\begin{array}{l}f(-6)=3 \Rightarrow-p \times 6^{7}-q \times 6^{3}-6 r-5=3 \\ f(6)=p \times 6^{7}+q \times 6^{3}+6 r-5=-\left(-p \times 6^{7}-q \times 6^{3}-6 r-5\right)-10=-3-10=-13\end{array}$