the answer is -$97 for sure.
1 {* S( |/ Z/ p( `TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。Think about it this way tvb now,tvbnow,bttvb: C* W1 m$ M# }8 i
1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)
$ R$ u/ j: L& J+ Z; C) m5 ^2) Now, the owner discovered that the 100 bucks is fake. You can think this as a lost of $100. therefore the overall gain is $3-$100 = -$97 |