A two-lane urban road with one-way traffic has a maximum capacity of $1800$ vehicles/hour. Under the jam condition, the average length occupied by the vehicles is $5.0 \: m$. The speed versus density relationship is linear. For a traffic volume of $1000$ vehicles/hour, the density (in vehicles/km) is

1. $52$
2. $58$
3. $67$
4. $75$