Given the task definition and input, reply with output. In this task, you will use your knowledge about language (and common sense) to determine what element the marked number refers to. The numbers are marked with two underlines around them, like: _ number _. Your answer should be chosen from the given text, and should not contain other words.

Tim Speedle: I got the GPS tracking signal from those two money bags , but it 's stationary . Now why would a guy who just robbed an armored truck be parked like a sitting duck ?
Lieutenant Horatio Caine: It 's possible because I put _ two _ in his gas tank .
Tim Speedle: You could have put two in him .
signal