11+1 NL Step 1 hand

[wAzZu24]

So a friend and i had a bit of an argument over this hand and id like some clarification.

3 players left, top 2 go on to step 2 and third is out.

Button is the big stack with 5780, SB is third with 1080 and BB is 2nd with 1140. SB posts 200, BB 400. The button raises enough to put either player all-in, and the SB calls all-in. You are the BB with A-3o, call or fold, and why?