Economics thats bothering me...

heres the case..

one gold flake king size cig s 5 rs

one pack 44rs

i buy a pack n think of returnin two to shopkeeper for 8rs

my loss: .80rs

shop key s gain: 2 rs

wat if i get 10rs for d 2 fags that i return??

my gain: 1.20 rs

shop keys loss: .80rs r 0rs???