the answer is -$97 for sure.
$ M5 d1 s0 V* ?8 q9 j1 `5 v6 p2 r& g公仔箱論壇Think about it this way 公仔箱論壇' V7 `! _$ a0 ~, M% L9 X" {
1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)
! x0 L: o7 d# m7 l8 hos.tvboxnow.com2) 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 |