the answer is -$97 for sure.
( ~# I. s( z8 i" P4 e0 f1 ?7 t7 l公仔箱論壇Think about it this way , U' R# c0 l8 {6 d
1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)/ C- t# ^6 N$ s5 a; L% Y
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 |