Explanation:

Use the Analyst agent for Prompt 1 because it is optimized for structured data work: consolidating worksheets, performing calculations, sentiment breakdowns by category (product line), and producing visualizations. These tasks align with analysis-style workflows where quantitative processing and charting are required.
Use the Researcher agent for Prompt 2 because it is designed to synthesize information from multiple sources, including SharePoint content plus web grounding , and to produce a well-structured brief with citations . Researcher is best when you need evidence-backed insights, reputable sourcing, and an organized narrative with risks and gaps.
Use Chat for Prompt 3 because the goal is drafting a refined executive email based on an attached document with tone control and communication standards. Chat excels at business writing, rewriting, tone adjustment, and producing polished communications without needing the deeper research workflow or heavy data analytics specialization.