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。/ y5 O2 U. p( B% }" O
Think about it this way ' g/ ]4 p/ T% f# K6 ]
1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)www2.tvboxnow.com- b. t! A% H, r7 Z
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 |