Early in Step 4

[parttimepro]

Party Step 4 single-table tournament. 3rd or 4th hand. Blinds are 10/15. No reads yet.
I get A[img]/images/graemlins/diamond.gif[/img]J[img]/images/graemlins/diamond.gif[/img] in MP. It's folded to me, and I raise to 50. All fold to BB, who calls.
Flop is Q[img]/images/graemlins/spade.gif[/img]T[img]/images/graemlins/spade.gif[/img]9[img]/images/graemlins/diamond.gif[/img]. Pot is 110. BB checks, and I bet 80. He calls.
Turn is 6[img]/images/graemlins/diamond.gif[/img]. Pot is 270. I now have both straight and flush draws. BB checks, I bet 200, he calls.
River is 6[img]/images/graemlins/heart.gif[/img]. BB checks. Pot is 670, and we both have 670 left. Push or check?