prozzy

the answer is -$97 for sure. 5.39.217.77; Q  m* D, z, W. u
Think about it this way
! P* W4 ]& l$ |: W# F% {. g" B8 J公仔箱論壇1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)/ U$ E' n( @4 _" q
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