the answer is -$97 for sure. TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。3 D7 H7 y9 u* F. P' l% `
Think about it this way - k$ J) y1 R+ Otvboxnow.com1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)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。' H/ w3 f2 M4 e5 b8 E
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