BT大皇

$2 bucks la,
( m3 F# g2 \; K9 x6 W' _assume he has $9 at the beginning, minus $8 for the first purchase and sold it for $9, his balance should be $10, then he used $10 to purchase, the balance is $0, afterward, he got $11 back, his final balance would be $11, $11 - $9 = $2 in total