he earn nth. cuz he sold it to the guy 9 bucks earn 1 dollar but when he buy it back with 10$he lost 1$.and when he sell it out when 11$ just got his money back !!he earn NOTHING they a raiseing the price up
$2 bucks la, # D" Q/ I$ M+ m7 X ?& }, y
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