Final answer:
The rung at shoulder height should be located about an arm's length away from the firefighter.
Step-by-step explanation:
In order to answer this question, we need to consider the optimal reach and range for a firefighter on a ladder. The rung at shoulder height should be located about an arm's length away from the firefighter. This allows the firefighter to maintain stability and balance while performing tasks. It also provides enough distance to ensure that the firefighter can safely reach objects or areas around them.