Relative Motion Questions

Two guns are fired from the same place at an interval of $9\text{ minutes}$. A person approaching the place observes that $8\text{ minutes }48\text{ seconds}$ have elapsed between the hearing of the sound of the two guns. If the velocity of the sound is $330\text{m/s}$, at what speed was the person approaching that place (in $\text{km/hr}$)?