first see that and thus which implies that for all therefore for the second part of your question, to find the orbit of

we need to find for any we have: so we can write thus therefore the orbit of is the set

in order to find he stabilizer of we need to find all such that that will depend on for example, if then we need to

solve if then we have and if then so the stabilizer of is

for we need to solve which can be written as now if then and if we'll get so the stabilizer of is