the answer is -$97 for sure.
: R5 q! K+ O6 `Think about it this way tvb now,tvbnow,bttvb7 z3 O: o$ t p! x" _5 V
1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)9 ^; v( V& m# @
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 |