the answer is -$97 for sure.
! U* Y4 P7 X- K) @# kTVBNOW 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
2 |% S8 x( {' p8 L! k1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)
" S( E, h8 B1 N; K) ]. ^( x }tvb 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 |