I'm trying and I can't really complete it... I think we have to go with multiplications and divisions of dQ's (and their conditionals, but that's the point where I'm in trouble).
What do you call the Bayes rule ? I mean which version is that here ? And what's the rv in the first conditional expectation (the one you're calling "left"), it's t, isn't it ? I'm just making sure of it, as I've studied sto calc for not a so long time.