1 EXHIBIT 11-13 DTE ENERGY COMPANY BASIC AND DILUTED EARNINGS PER SHARE OF COMMON STOCK Three Months Nine Months Ended Ended September 30, 1998 September 30, 1998 ------------------ ------------------ (Thousands, except per share amounts) BASIC: Net Income......................................$ 132,037 $ 336,637 Weighted average number of common shares outstanding (a)........................ 145,075 145,078 Earnings per share of Common Stock based on weighted average number of shares outstanding.........................$ 0.91 $ 2.32 DILUTED: Net Income......................................$ 132,037 $ 336,637 Weighted average number of common shares outstanding (a)........................ 145,075 145,078 Incremental shares from assumed exercise of options.................................... 116 95 ---------- ----------- 145,191 145,173 ========== =========== Earnings per share of Common Stock assuming exercise of options..................$ 0.91 $ 2.32 - ------------------------------------------------------ (a) Based on a daily average.