Hull-White Trinomial tree probabilities

I just want to confirm if we can be asked to construct the H-W trinomial tree for the short-rate and consequently if we need to remember the pu, pd and pm formulas for all the three branching methods?

 

SORTED, I can now derive all of them without much effort i.e Figures a) b) and c).

 

No, I don't think you'd be expcted to know these formulae.

 

Yeah, just worked this out myself. It's actually straightforward - and it gives more understanding about the H&W itself. I'm entering panic mode now with slightly more than 2 months to get more of these things sorted out!