An aerial photograph is taken from a flight at a height of $3.5$ $\text{km}$ above mean sea level, using a camera of focal length $152$ $\text{mm}$. If the average ground elevation is $460 \:m$ above mean sea level, then the scale of the photograph is

1. $1 : 20000$
2. $1 : 20$
3. $1 : 100000$
4. $1 : 2800$