the answer is -$97 for sure.
: h M2 k# W* _- R% @Think about it this way # V1 Q2 V- F, `9 D8 J( \0 _
1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)
1 C7 R4 ^( f/ m6 @6 ]3 Y2) 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 |