I have a 2008 Scion xB- can it fit 3 Carseats in it?

We purchased an 08' Scion Hb 3 months ago & so far I love it. Only problem is the interior is a pain to keep clean with 2 kids. We are currently thinking of having another child and can't afford to upgrade to a van right now- yeah we should have thought about this before buying. Anyways I was wondering if anyone knows if you can fit 3 carseats in the back, we have a 4 almost 5 year old who is in a backless booster, and our daughter is 3 and in a convertible carseat- Evenflo Triumph. If you can fit 3 which seem to work the best????