A person travels a certain distance at $5 \; \text{km/hr}$ and reaches $10$ min late. If he travels at $6 \; \text{km/hr}$, he reaches $10$ min earlier. The distance he has to travel is :

- $6 \; \text{km}$
- $7.2 \; \text{km}$
- $8 \; \text{km}$
- $10 \; \text{km}$