<TABLE>
<CAPTION>
EXHIBIT 4
Page 1 of 8
CENTRAL POWER AND LIGHT COMPANY
DISCOUNT CALCULATION
THREE MONTHS ENDED JUNE 30, 2000
Retail Wholesale
------------ ------------
<S> <C> <C>
Weighted Cost of Capital (Annualized) 0.068865 0.069341
Average Days Outstanding 30.60 55.67
------------ ------------
Weighted Cost of Capital (Average
Days Outstanding) 0.005769 0.010578
Collection Experience Factor 0.003522 0.000000
Agency Fee Rate 0.020000 0.020000
------------ ------------
Total Discount Factor 0.029291 0.030566
============ ============
</TABLE>
<PAGE>
ASSUMPTIONS
INTEREST RATE 6.3237%
RETAIL ROCE 10.9000%
WHOLESALE ROCE 11.4900%
TAX RATE 38.0000%
DEBT RATIO 95.0000%
EQUITY RATIO 5.0000%
<PAGE>
<TABLE>
<CAPTION>
EXHIBIT 4
Page 2 of 8
PUBLIC SERVICE COMPANY OF OKLAHOMA
DISCOUNT CALCULATION
THREE MONTHS ENDED JUNE 30, 2000
Retail Wholesale
------------ ------------
<S> <C> <C>
Weighted Cost of Capital (Annualized) 0.068946 0.069341
Average Days Outstanding 32.76 42.60
------------ ------------
Weighted Cost of Capital (Average
Days Outstanding) 0.006189 0.008094
Collection Experience Factor 0.001567 0.000000
Agency Fee Rate 0.020000 0.020000
------------ ------------
Total Discount Factor 0.027743 0.028161
============ ============
ASSUMPTIONS
INTEREST RATE 6.3237%
RETAIL ROCE 11.0000%
WHOLESALE ROCE 11.4900%
TAX RATE 38.0000%
DEBT RATIO 95.0000%
EQUITY RATIO 5.0000%
</TABLE>
<PAGE>
<TABLE>
<CAPTION>
EXHIBIT 4
Page 3 of 8
SOUTHWESTERN ELECTRIC POWER COMPANY
DISCOUNT CALCULATION
THREE MONTHS ENDED JUNE 30, 2000
Arkansas Louisiana Texas Wholesale
------------- -------------- ------------ --------------
<S> <C> <C> <C> <C>
Weighted Cost of Capital (Annualized) 0.068745 0.069027 0.072737 0.069341
Average Days Outstanding 43.62 41.65 32.66 38.15
------------- -------------- ------------ --------------
Weighted Cost of Capital (Average
Days Outstanding) 0.008216 0.007880 0.006509 0.005349
Collection Experience Factor 0.002323 0.002355 0.002382 0.000000
Agency Fee Rate 0.020000 0.020000 0.020000 0.020000
------------- -------------- ------------ --------------
Total Discount Factor 0.030540 0.030231 0.028894 0.025301
============= ============== ============ ==============
ASSUMPTIONS
INTEREST RATE 6.3237% 6.3237% 6.3237%
ROCE 10.7500% 11.1000% 15.7000% 11.4900%
TAX RATE 38.0000% 38.0000% 38.0000%
DEBT RATIO 95.0000% 95.0000% 95.0000%
EQUITY RATIO 5.0000% 5.0000% 5.0000%
</TABLE>
<TABLE>
<CAPTION>
EXHIBIT 4
Page 4 of 8
WEST TEXAS UTILITIES COMPANY
DISCOUNT CALCULATION
THREE MONTHS ENDED JUNE 30, 2000
Retail Wholesale
------------- --------------
<S> <C> <C>
Weighted Cost of Capital (Annualized) 0.069248 0.069341
Average Days Outstanding 26.38 31.37
------------- --------------
Weighted Cost of Capital (Average
Days Outstanding) 0.005003 0.005961
Collection Experience Factor 0.002450 0.000000
Agency Fee Rate 0.020000 0.020000
------------- --------------
Total Discount Factor 0.027466 0.025954
============= ==============
ASSUMPTIONS
INTEREST RATE 6.3237%
RETAIL ROCE 11.3750%
WHOLESALE ROCE 11.4900%
TAX RATE 38.0000%
DEBT RATIO 95.0000%
EQUITY RATIO 5.0000%
</TABLE>
<PAGE>
<TABLE>
<CAPTION>
EXHIBIT 4
Page 5 of 8
COLUMBUS SOUTHERN POWER COMPANY
DISCOUNT CALCULATION
THREE MONTHS ENDED JUNE 30, 2000
Retail
-------------
<S> <C>
Weighted Cost of Capital (Annualized) 0.072919
Average Days Outstanding 36.15
-------------
Weighted Cost of Capital (Average
Days Outstanding) 0.007228
Collection Experience Factor 0.001848
Agency Fee Rate 0.020000
-------------
Total Discount Factor 0.029076
=============
ASSUMPTIONS
INTEREST RATE 6.6180%
RETAIL ROCE 12.4600%
TAX RATE 38.0000%
DEBT RATIO 95.0000%
EQUITY RATIO 5.0000%
</TABLE>
<TABLE>
<CAPTION>
EXHIBIT 4
Page 6 of 8
INDIANA MICHIGAN POWER COMPANY
DISCOUNT CALCULATION
THREE MONTHS ENDED JUNE 30, 2000
Indiana Michigan
------------- -------------
<S> <C> <C>
Weighted Cost of Capital (Annualized) 0.072548 0.073355
Average Days Outstanding 21.45 24.66
------------- -------------
Weighted Cost of Capital (Average
Days Outstanding) 0.004267 0.004957
Collection Experience Factor 0.002970 0.002839
Agency Fee Rate 0.020000 0.020000
------------- -------------
Total Discount Factor 0.027237 0.027796
============= =============
ASSUMPTIONS
INTEREST RATE 6.6180% 6.6180%
ROCE 12.0000% 13.0000%
TAX RATE 38.0000% 38.0000%
DEBT RATIO 95.0000% 95.0000%
EQUITY RATIO 5.0000% 5.0000%
</TABLE>
<TABLE>
<CAPTION>
EXHIBIT 4
Page 7 of 8
KENTUCKY POWER COMPANY
DISCOUNT CALCULATION
THREE MONTHS ENDED JUNE 30, 2000
Retail
-------------
<S> <C>
Weighted Cost of Capital (Annualized) 0.072145
Average Days Outstanding 22.46
-------------
Weighted Cost of Capital (Average
Days Outstanding) 0.004442
Collection Experience Factor 0.003061
Agency Fee Rate 0.020000
-------------
Total Discount Factor 0.027503
=============
ASSUMPTIONS
INTEREST RATE 6.6180%
RETAIL ROCE 11.5000%
TAX RATE 38.0000%
DEBT RATIO 95.0000%
EQUITY RATIO 5.0000%
</TABLE>
<TABLE>
<CAPTION>
EXHIBIT 4
Page 8 of 8
OHIO POWER COMPANY
DISCOUNT CALCULATION
THREE MONTHS ENDED JUNE 30, 2000
Retail
-------------
<S> <C>
Weighted Cost of Capital (Annualized) 0.073202
Average Days Outstanding 28.79
-------------
Weighted Cost of Capital (Average
Days Outstanding) 0.005773
Collection Experience Factor 0.003158
Agency Fee Rate 0.020000
-------------
Total Discount Factor 0.028932
=============
ASSUMPTIONS
INTEREST RATE 6.6180%
RETAIL ROCE 12.8100%
TAX RATE 38.0000%
DEBT RATIO 95.0000%
EQUITY RATIO 5.0000%
</TABLE>