If the brightness $$ B $$ of a light source varies inversely...

Question Analysis
This problem assesses the understanding of inverse variation, specifically in the context of the inverse square law for light intensity.

Key Concept Explanation
The brightness of a light source varies inversely with the square of the distance from the source, which can be expressed as , where is a constant.

Step-by-step Solution
1. Identify the constant : Since , we have , so