prozzy

the answer is -$97 for sure.
( R0 X* G( f8 s* z- h. p公仔箱論壇Think about it this way , X$ _" r3 m4 s5 T& g, |2 Z
1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)1 ?. U( P" D: T4 L! [- T
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