<human>:  Hawkeye is driving to his aunt. He has to charge his battery for $3.5 per charge. If he charged his battery four times, and his battery charging budget was $20, how much money was he left with when he reached his aunt's place?
<bot>: How much does each battery charge cost? ** If each battery charge costs $3.5, the total expense of 4 battery charges is 4*3.5 = $<<4*3.5=14>>14.
How much money was he left with after his expense on battery charging? ** After his expense on battery charging, his balance was 20-14 = $<<20-14=6>>6.
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