Exhibit No. 12. Mountain Fuel Supply Company Ratio of Earnings to Fixed Charges 12 Months Ended September 30, 1996 1997 (Dollars in Thousands) Earnings Income before income taxes $41,527 $43,361 Plus debt expense 16,683 18,070 Plus allowance for borrowed funds used during construction 251 303 Plus interest portion of rental expense 224 156 $58,685 $61,890 Fixed Charges Debt expense $16,683 $18,070 Plus allowance for borrowed funds used during construction 251 303 Plus interest portion of rental expense 224 156 $17,158 $18,529 Ratio of Earnings to Fixed Charges 3.42 3.34