9. Phosphorus is a critical nutrient for sustaining plant and animal life. Phosphorus for crop fertilizer is mined from certain rock deposits, primarily in the United States, China, Morocco, and Tunisia. Examine the plot below of worldwide production of mined rock phosphorus (megatons, MT), since 1900 (Scholz and Wellmer, Global Environmental Change, 2013, 23 (1), 11-27). Answer the following questions based on your analysis of the phosphorus plot: a. What resource production model is appropriate for the world production of mined rock phosphorus? Why? b. When do you estimate that peak rock phosphate production occurs? At what peak production? c. Based on your production model, what will be the total amount (MT) of rock phosphorus mined worldwide? Use the following assumptions, as appropriate, for your production model: r= 1.0%; g = 25 years. 180 (a) 160 140 120 MW 100 Production (MT) BO 60 40 20 1900 1925 1950 1975 2000 2025 2050 Year