so every minute cost 8 cents so i toke the 20$ and kept subtracting 8 cents from it until i got to 16.14 and i knew i couldn't subtract another 8 cents because that would've been below 16.16 so i just added 2 sec and it gave me 16.16 and i counted all of the minutes. i hope i gave u the right answer because i tried and i´m very bad at math lol.