the answer is -$97 for sure.
1 C3 p; z7 f3 _# W: qThink about it this way
$ z5 [' [* w: v3 W2 s, e5.39.217.771) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)公仔箱論壇. V! c4 N' w; R$ l6 T
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 |