the answer is -$97 for sure. % d g5 n* L' y# [5 P
Think about it this way
+ n( S' G9 \- \6 _! j ^7 d1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)
2 v2 t( f; w6 y. |$ h- C' ^5.39.217.772) 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 |