We are doing a case study on Pfizer. Can you conduct time-series and/or cross-sectional analyses, and discuss the trend of Pfizer's ROA and ROCE in the past 3-5 years; and how Pfizer performed in this period compared to its major competitors (Merck) and average firms of the same industry sector. Please link this discuss with your strategy and industry analysis, tell the audience what economic and strategic factors that help explain the results of your ROA and ROCE ratios.