MDU RESOURCES GROUP, INC. COMPUTATION OF RATIO OF EARNINGS TO FIXED CHARGES AND COMBINED FIXED CHARGES AND PREFERRED STOCK DIVIDENDS Twelve Months Year Ended Ended March 31, 1998 December 31, 1997 (In thousands of dollars) Earnings Available for Fixed Charges: Net Income per Consolidated Statements of Income $ 57,814 $ 54,617 Income Taxes 32,012 30,743 89,826 85,360 Rents (a) 1,435 1,249 Interest (b) 32,470 33,047 Total Earnings Available for Fixed Charges $123,731 $119,656 Preferred Dividend Requirements $ 781 $ 782 Ratio of Income Before Income Taxes to Net Income 155% 156% Preferred Dividend Factor on Pretax Basis 1,211 1,220 Fixed Charges (c) 33,905 34,296 Combined Fixed Charges and Preferred Stock Dividends $ 35,116 $ 35,516 Ratio of Earnings to Fixed Charges 3.7x 3.5x Ratio of Earnings to Combined Fixed Charges and Preferred Stock Dividends 3.5x 3.4x (a) Represents portion (33 1/3%) of rents which is estimated to approximately constitute the return to the lessors on their investment in leased premises. (b) Represents interest and amortization of debt discount and expense on all indebtedness and excludes amortization of gains or losses on reacquired debt which, under the Uniform System of Accounts, is classified as a reduction of, or increase in, interest expense in the Consolidated Statements of Income. Also includes carrying costs associated with natural gas available under a repurchase agreement with Frontier Gas Storage Company as more fully described in Notes to Consolidated Financial Statements. (c) Represents rents and interest, both as defined above.