Which one of the following e–mail messages CANNOT be from Lula?

Kadeem on July 7, 2020

Help please

Can I get an explanation for the setup and how the answer is 6

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Shunhe on July 8, 2020

Hi @Harper,

Thanks for the question! So here, we’re being asked for which email message cannot be from L. Now answer choice E is the correct answer and it says that the 6th message can’t be from L. Why not? Well, take a look at the second rule, which tells us that the first and last messages are from the same person. So since Sukanya gets at most 6 emails, if there are 6 emails, the 6th email is the last one. And whoever sends that email has to be the same person who sends the first email. Now take a look at the first rule, which tells us that L doesn’t send the first message. Well, if L can’t send the first email, the L can’t send the last email, since the same person has to send the first and last emails. So if there are 6 emails, which is the max, then L can’t send the 6th, since that’s the last email.

As for a setup, we know that there will be somewhere between 4 and 6 slots, and that only H and J can leave the first and last messages. So you could diagram this like

H/J __ __ H/J

H/J __ __ __ H/J

H/J __ __ __ __ H/J

And then we know there’s an HJ block that occurs exactly once, and that J appears in the first three blocks, so we can add those rules in too.

Hope this helps! Feel free to ask any other questions that you might have.