This looks pretty good what you have calculated in terms of the tree.
Also when you say the probability that the Competition Tribunal accepts it, are you finding all probabilities of it not being rejected in any branch?
If this is the case, then you need to look at all possibilities where it is approved and add up these possibilities (you can do this because all events are disjoint from each other). If the above is the case you have five ways of getting accepted which means you have to calculate five probabilities.
Have you covered how to calculate probabilities given a probability tree?