Doctor Yamata

Hi @Anna2020, Happy to help! We know that Dr. Y works five days of the week: M, T, W, F, and S. On these days, she performs four different activities: L, O, P, and R. She performs exactly one activity in the morning and exactly one activity in the afternoon. AM: _ _ _ _ _ PM: _ _ _ _ _ M T W F S Now let's go through our conditions. Rule 1 - Dr. Y performs O exactly three mornings during the week. Rule 2 - If Dr. Y performs O on M, she does not perform O on T. OM --> Not OT OT --> Not OM Rule 3 - Dr. Y does L in the afternoon on exactly two consecutive calendar days. Rule 4 - Dr. Y treats P on exactly one morning and exactly three afternoons. Rule 5 - Dr. Y conducts R on exactly one morning. Rule 6 - Dr. Y neither does L nor performs O on Saturday. This means that Dr. Y can only conduct R or treat P on Saturday. We now know the activities which must take up all 10 slots of Dr. Y's time during the week. We just don't know what order they go in. Morning Activities: O O O P R Afternoon Activities: L L P P P We do know that Dr. Y cannot perform O on S and Rule 2 tells us that she cannot perform O on both M and T. Therefore, we have two options for Dr. Y's mornings. Option 1 AM: O R/P O O P/R M T W F S Option 2 AM: R/P O O O P/R M T W F S We also know that Dr. Y does L in the afternoon on exactly two consecutive days which cannot be Saturday. Therefore, we have three options. Option 1 PM: L L P P P M T W F S Option 2 PM: P L L P P M T W F S Option 3 PM: P P L L P M T W F S We are looking for the answer choice which MUST be true. Answer choice (C) could be true, but it does not have to be true. Why? Because pairing Option 1 AM and Option 1 PM gives us a schedule where Dr. Y does not conduct R on a day where she treats P. Notice that there is nothing that says Dr. Y must perform two different activities each day. Therefore, there is no reason why Dr. Y cannot treat P all day Saturday. AM: O R O O P PM: L L P P P M T W F S The only day on which Dr. Y conducts R is a day when she does L. Notice that this meets all of our conditions: 1) Dr. Y performs O on M, W, and F mornings. 2) Dr. Y performs O on M and does not perform O on T. 3) Dr. Y does L on M and T afternoons. 4) Dr. Y treats P on F morning and on W, F, and S afternoons. 5) Dr. Y conducts R on T morning. 6) Dr. Y only treats P on S; she neither does L nor performs O on this day. On the other hand, answer choice (E) must be true because it is impossible to design a schedule where Dr. Y does not L on the same day that she performs O. Starting with AM Option 1, O and L overlap on: PM Option 1 - Monday PM Option 2 - Wednesday PM Option 3 - Wednesday and Friday Now moving to AM Option 2, O and L overlap on: PM Option 1 - Tuesday PM Option 2 - Tuesday and Wednesday PM Option 3 - Wednesday and Friday Hope this helps! Please let us know if you have any further questions.