115:2 should be the correct answer in reduced form.
Actually, this has little to do with mathematics and geometry but has to do more with logical reasoning. You have two clauses to get a conclusion from. The reasoning is as follows:
Clause 1: <span>Three noncollinear points determine a plane
Clause 2: </span><span>Points S, O, N are noncollinear
</span>Conclusion: Therefore, points S, O and N form a plane.
