Final answer:
The primary business segmentation variable is product use. Business geography influences economic activity location decisions, cost, and operational efficiency.
Step-by-step explanation:
The primary business segmentation variable in the scenario described where Bethlehem Steel prepares steel differently for its customers based on how they will use it in their production processes is product use. Business segmentation involves categorizing parts of the market based on shared characteristics; in this case, it is the specific requirements of the steel by different customers for their unique production needs. Business geography plays a crucial role in the location of economic activities and can significantly impact operational costs and efficiency for companies like Bethlehem Steel. For instance, depending on whether an industry is bulk gaining or bulk reducing, it may choose to locate its production facilities closer to raw materials or markets, respectively.