Final answer:
To represent the analysis of increased sales due to an automated book recommendation system, a line graph or a bar graph would be the most suitable tools. Line graphs track trends over time, while bar graphs compare categories or show changes over time, both being appropriate for this sales analysis.
Step-by-step explanation:
To analyze whether the automated system for referring books to customers based on their buying history is resulting in increased sales, the appropriate tool to visually represent this analysis would be a line graph or a bar graph.
Since the scenario implies a desire to understand changes over time, line graphs are particularly useful for displaying data trends and variations over a period, making it easier to track the sales increase or decrease. A bar graph, on the other hand, is more suited for comparing categories or showing changes over time as well. It allows us to see differences in sales figures before and after implementing the automated system.
While pie charts are great for showing parts of a whole at a single point in time, and making comparisons between categories, they are less helpful when trying to understand trends or changes over time, which is what is required in this analysis.