the answer is -$97 for sure.
$ m8 K, N7 Z% t5 b0 |* d4 S( `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 5.39.217.772 ]# Z* v1 C" C" b* Q7 n) B
1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)公仔箱論壇8 g& P1 W; a. D) u
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 |