The molecular weight data for a polypropylene material are tabulated and shown in the table below. Compute the number-average molecular weight. Table Molecular Weight Data Molecular Weight Xi Wi Range (g/mol) 8,000- 0.05 0.02 16,000 16,000- 0.16 0.10 24,000 24,000- 0.24 0.20 32,000 32,000- 0.28 0.30 40,000 40,000- 0.20 0.27 48,000 48,000- 0.07 0.11 56,000 45,050 g/mol O 17,850 g/mol O33,040 g/mol 21,150 g/mol 31,200 g/mol O 36,240 g/mol