Question 1155874
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72 - 40 = 32 minutes of the phone call cost  15.20-11.36 = 3.84 dollars, giving the rate of  {{{3.84/32}}} = 0.12 dollars per minute.


So, after 86 minutes the amount on the card will be  15.20 - (86-40)*0.12 = 9.68 dollars.
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Solved.