the answer is -$97 for sure. & u# T. x# Q2 W5 I0 nThink about it this way 公仔箱論壇. e! ^5 ?" e4 g ]8 v0 o
1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)公仔箱論壇- z: B9 R. ~; M- f9 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