18. [Disaggregation of ROE, effects of operating leverage] The following data were taken from Texaco's 1997-1999 an- nual reports. Selected Data for Texaco, 1997-1999 (Smillions) 1997 1998 1999 Sales $45,187 $30,910 $34,975 EBIT (earnings before 3,847 1.124 2,083 interest and tax) Pretax income 3.327 701 1.779 Net income 2.664 603 1,177 Assets Equity 29.600 28,570 28,972 12,766 11,833 12,042

a. Calculate Texaco's ROE (return on equity) for 1997-1999.