the answer is -$97 for sure.
3 n3 q+ \& p5 U" }& @+ T$ U公仔箱論壇Think about it this way
; Z+ G* S8 z% }- I+ l! p7 }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。1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)tvb now,tvbnow,bttvb( A* k( n) `9 E8 `7 _
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 |