>>> from ebill import ebill_eval

--ini

>>> ebill_eval(10.0, 3.0, 200, 1)
1950

>>> ebill_eval(7.0, 3.0, 200, 2)
1500

>>> ebill_eval(7.0, 3.0, 50, 3)
450

>>> ebill_eval(7.0, 3.0, 9, 2)
90

--fi

>>> ebill_eval(10.0, 6.0, 300, 1)
2550

>>> ebill_eval(6.0, 10.0, 300, 2)
2550

>>> ebill_eval(10.0, 6.0, 50, 1)
500

>>> ebill_eval(6.0, 10.0, 50, 2)
500

>>> ebill_eval(7.0, 3.0, 200, 6)
750

>>> ebill_eval(6.0, 10.0, 300, 7)
1275