the answer is -$97 for sure.
$ p% @) Z+ j0 \' MThink about it this way tvb now,tvbnow,bttvb0 y* e9 k, y$ q
1) if the 100 bucks is not a fake one, the store owner will gain $3 ($21-$18)
; ^1 m- X# Q9 E2 V公仔箱論壇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 |