We could probably call this a group game, but what really matters are the initial endowments and the exchange rates. We know that each building can be traded, and that cat 1 = 2 cat 2, and cat 2 equals 2 cat 3. We know that each company must only make trades according to this formula, so we need for figure out the initial endowments. We can assign values to each building type: cat 1 is worth four cat threes, cat two is worth two cat threes, and cat three is worth one. Thus
R = 6 S= 6 T= 6
Any scenario that preserves this distribution using valid trades is valid.
For this question we are looking for evidence of an invalid trade: we can find this by showing the value of one of them is not six.
