the answer is -$97 for sure.
9 P7 z7 }( x2 o' qThink about it this way 5.39.217.77& t1 ^) ~ { }5 [8 p
1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)5.39.217.77$ |( @) z; K/ y; c5 `' P/ e
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 |