G6.1 If $12345 \times 6789=a \times 10^{p}$ where $p$ is a positive integer and $1 \leq a<10$, find $p$.
$\begin{array}{l}12345 \times 6789=1.2345 \times 10^{4} \times 6.789 \times 10^{3}=a \times 10^{7}, \\ \text { where } a=1.2345 \times 6.789 \\ \quad \approx 1.2 \times 6.8=8.16 \\ 1 \leq a<10 \\ p=7\end{array}$