the answer is -$97 for sure.
' J5 A% p- N- L公仔箱論壇Think about it this way
; F' k9 E( M+ n2 W' t2 t- L# T公仔箱論壇1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)
# x# I! _, d- @/ r7 T2) 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 |