Let's start from the beginning, with only our initial diagrams, and try to answer Question 6. One of the first things I did was create two diagrams based on this rule:
"Exactly one of Larisa's aisles is an end aisle."
This means Larisa stocks either 1 and not 9, or 9 and not 1.
1. L K _ _ _ _ _ _ J
In this diagram, Larisa cannot stock 9. But how did I place J there? Think about who else cannot stock aisle 9. O can't, it must go before L. K can't, it must be surrounded by M. M can't, this would leave no room for O to come after both K's. We are left only with J.
2. J K _ _ _ _ _ _ L
In this diagram, Larissa cannot stock 1. How did I place J there? We know that M can't stock 1 from rule 3. We know that O has to come after both K's. We know it cannot be K, because it must be surrounded by M's. We are left with J.
Now that we have these two setups, we can check the answer choices. The key is to try to place that MKM block. Remember that O must come after this block, and so must at least one L. Make sure there is room for both.
1. L K J _ _ _ _ _ J
2. J K J _ _ _ _ _ L
A. This could be true in Diagram 1. B. This is possible in Diagram 2. C. Possible in Diagram 2. D. Possible in either diagram. E. If Olga stocks 6, there is no room for the MKM block. This is the correct answer.
I'm guessing that you believed 4 and 5 were necessary to answer 6 because you built up some of these inferences as you moved through the questions. This is totally fine, and it is good to learn things as we go. However, the information that placed J and L in my diagrams was available from the beginning. Try to make a note of where variables cannot go, this can reveal some critical inferences.
