Thanks for the question! So in this question you commented on, it’s actually completely possible for T to have traded exclusively with R. And actually, T could’ve traded in exactly the way you mentioned. Trading a class 2 for the two class 3s, and trading two class 2s for the class 1. But even if this is true, (E) is correct; T owns the Zimmer House. And that’s through trading for the Zimmer House and the Yates House from Realprop. There’s no way around that, since at the end, T won’t have any class 2 buildings, which means that T will have to have 1 class one building and 2 class two buildings. This is because if you think of Class 1 being worth 4 units, Class 2 being worth 2 units, and Class 3 being worth 1 unit, T has to end up with 6 total units; since it can’t have any Class 2s, and there aren’t 6 Class 1s, it has to have 4+1+1 units.
Hope this helps! Feel free to ask any other questions that you might have.