<PAGE>
<TABLE>
Exhibit 12a

                      STATEMENT SETTING FORTH COMPUTATIONS OF RATIOS OF
                                 EARNINGS TO FIXED CHARGES
                                   (Dollars in Thousands)
<CAPTION>
                                12 Months
                                   Ending                Year Ended December31
                                September  ------------------------------------------------
                                 30, 1997      1996      1995      1994      1993      1992
                                ---------  ------------------------------------------------
<S>                             <C>        <C>       <C>      <C>        <C>       <C>
EARNINGS AVAILABLE FOR
 FIXED CHARGES
  Pre-tax income:
    Income from continuing
      operations per statement
      of income                  $143,904  $167,351  $128,382  $ 79,312  $163,812  $153,942
    Federal income taxes           48,872   107,747    91,519    74,816    93,702    76,114
    Federal income taxes charged
      to other income - net        11,871    (1,608)  (12,068)   22,687      (418)   (1,781)
    Capitalized interest             (540)     (600)     (660)     (400)     (791)   (1,205)
    Undistbuted (earnings) or
      losses of less-than-
      fifty-percent-owned
      entities                     (1,059)      460     8,325       743        --      (567)
                                 --------  ------------------------------------------------
      Total                      $203,048  $273,350  $215,498  $177,158  $256,305  $226,503

  Fixed charges:
    Interest expense             $123,429  $122,635  $131,346  $126,555  $120,962  $131,029
    Other interest                    540       600       660       400       791     1,205
    Portion of rentals
      representative of the
      interest factor               3,635     4,187     5,150     5,555     5,570     5,991
                                 --------  ------------------------------------------------
      Total                      $127,604  $127,422  $137,156  $132,510  $127,323  $138,225

  Earnings available for
    combined fixed charges       $330,652  $400,772  $352,654  $309,668  $383,628  $364,728
                                 ========  ================================================
RATIO OF EARNINGS TO
  FIXED CHARGES                     2.59x     3.15x     2.57x     2.34x     3.01x     2.64x

</TABLE>
<PAGE>
<TABLE>
Exhibit 12b

                     STATEMENT SETTING FORTH COMPUTATIONS OF RATIOS OF
             EARNINGS TO COMBINED FIXED CHARGES AND PREFERRED STOCK DIVIDENDS
                                   (Dollars in Thousands)
<CAPTION>
                                12 Months
                                   Ending                Year Ended December 31
                                September  ------------------------------------------------
                                 30, 1997      1996      1995      1994      1993      1992
                                ---------  ------------------------------------------------
<S>                             <C>        <C>       <C>       <C>      <C>        <C> 
EARNINGS AVAILABLE FOR COMBINED
 FIXED CHARGES AND PREFERRED
 DIVIDEND REQUIREMENTS

  Pretax income:
    Income from continuing
      operations per statement
      of income                  $143,904  $167,351  $128,382  $ 79,312  $163,812  $153,942
    Federal income taxes           48,872   107,747    91,519    74,816    93,702    76,114
    Federal income taxes charged
      to other income - net        11,871    (1,608)  (12,068)   22,687      (418)   (1,781)
                                 --------  ------------------------------------------------
      Subtotal                    204,647   273,490   207,833   176,815   257,096   228,275
  Capitalized interest               (540)     (600)     (660)     (400)     (791)   (1,205)
  Undistributed (earnings) or
    losses of less-than-fifty-
    percent-owned entities         (1,059)       460    8,325       743        --      (567)
                                 --------  ------------------------------------------------
      Total                      $203,048  $273,350  $215,498  $177,158  $256,305  $226,503

  Fixed charges:
    Interest expense             $123,429  $122,635  $131,346  $126,555  $120,962  $131,029
    Other interest                    540       600       660       400       791     1,205
    Portion of rentals
      representative of the
      interest factor               3,635     4,187     5,150     5,555     5,570     5,991
                                 --------  ------------------------------------------------
      Total                      $127,604  $127,422  $137,156  $132,510  $127,323  $138,225

Earnings available for
  combined fixed charges
  and preferred dividend
  requirements                   $330,652  $400,772  $352,654  $309,668  $383,628  $364,728
                                 ========  ================================================

DIVIDEND REQUIREMENT:
  Fixed charges above            $127,604  $127,422  $137,156  $132,510  $127,323  $138,225
  Preferred dividend
    requirements below             28,526    36,249    36,674    45,441    29,904    24,476
                                 --------  ------------------------------------------------
      Total                      $156,130  $163,671  $173,830  $177,951  $157,227  $162,701
                                 ========  ================================================
</TABLE>
<PAGE>
<TABLE>
<CAPTION>
                                12 Months
                                   Ending                Year Ended December 31
                                September  ------------------------------------------------
                                 30, 1997      1996      1995      1994      1993      1992
                                ---------  ------------------------------------------------
<S>                              <C>       <C>      <C>        <C>      <C>        <C>           
RATIO OF EARNINGS TO COMBINED
  FIXED CHARGES AND PREFERRED
  DIVIDEND REQUIREMENTS              2.12      2.45      2.03      1.74      2.44      2.24

COMPUTATION OF PREFERRED
  DIVIDEND REQUIREMENTS:
  (a) Pre-tax income             $204,647  $273,490  $207,833  $176,815  $257,096  $228,275
  (b) Income from continuing
        operations               $143,904  $167,351  $128,382  $ 79,312  $163,812  $153,942
  (c) Ratio of (a) to (b)          1.4221    1.6342    1.6189    2.2294    1.5695    1.4829
  (d) Preferred dividends        $ 20,059  $ 22,181  $ 22,654  $ 20,383  $ 19,054  $ 16,506
  Preferred dividend
    requirements
      [(d) multiplied by (c)]    $ 28,526  $ 36,249  $ 36,674  $ 45,441  $ 29,904  $ 24,476
                                 ========  ================================================
</TABLE>