This question places N fourth. When a question gives you a new rule, you should consider which of the existing rules apply.
From the main diagram, we know that N and S can’t go together. So, you can draw a not rule for S on Wednesday and Friday:
Friday is the most restricted, so you should think who else can’t go there. Rule 3 tells us L can only go on Wednesday, so it’s out. And obviously N can’t go Friday – it’s Thursday:
So there are five variables which can’t go Friday. Who’s left? Only P. D is CORRECT.
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