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。% M* F) G- ~& q) I; S
Think about it this way ; f* N; z6 q3 V0 Z
1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)
8 W, Z+ t$ D+ S8 H, dtvb now,tvbnow,bttvb2) 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 |