If a sixth brand M is tested and found to be more effective than S, then which of the following must be true, if the findings of the study are correct?

According to the question,
P > Q. S > R
T is least effective Q = R, S > Q
∴ S/P > Q = R > T
It is clear from the ranking order so obtained that brand S may be less effective than P, equal to P or more effective than P. It means that position of S is not fixed. Now as per question, sixth band i.e, M is more effective than S which implies that whatever be the position of S, there will be atleast four brands which will be less effective than M.