Ruling - How many chips in play?

[ATrebek]

$1/3 NL game. Player's A, B, and C to the flop. Player B's stack is 100, player C's stack is 150. Player A checks, player B goes all, player C goes all in over the top.

Meanwhile, player A has been racking his chips to move to another game and has mixed his chips in with more chips that aren't in play (about $500 total), but decides he wants to call. No one is sure how many chips player A had on the table when the hand started, but it was "probably around $100" according to player A.

How much does it cost player A to call?

Floor ruled on this hand, but I want to hear other's opinions before I say what they ruled.

Player A gets a KITN, obv.