Question 491034
You don't need a graph other than to confirm that PQRS is in order going aroung the thing.
You don't need to assume all numbers are positive, but doing so helps you visualize a standard case.
The answer will still work if some of the abc are negative.
In teh All-Positive case, you will see that R is the rightmost and S to its left:
R is (a+b,c).