the answer is -$97 for sure.
( f7 f% W1 Q, f4 A2 M/ `公仔箱論壇Think about it this way
6 @+ e7 F2 \% |/ F0 y! b5.39.217.761) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)公仔箱論壇, f7 Y3 G, [$ f/ W' @% x; k6 z4 R
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 |