the answer is -$97 for sure.
. [) f6 {# B9 e3 t0 P- IThink about it this way 公仔箱論壇0 b& N6 g5 J! @! E- `) Y
1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18). R i" `8 ?6 F# L# G4 F
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 |