the answer is -$97 for sure.
) E" |+ P; c5 q! s2 u0 X$ rtvb now,tvbnow,bttvbThink about it this way 公仔箱論壇; S" m s, c% X \! y$ H
1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。( @$ c1 q* d4 Z* E- Q
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 |