The manager is concerned about the average time for getting an order ready for pick-up (either by a full-service shopper or the customer). Please note that this includes both the time duration from the arrival of the order to the moment it starts to be processed by a shopper, and the processing time (shopping, checkout, and moving to the staging area). She finds that it is difficult to change the order arrival pattern or the processing speed of the in-store shoppers, and decides to check if they can potentially reduce the time by changing the number of in-store shoppers.

To reduce the average time for getting an order ready below 60 minutes, at least how many in-store shoppers are required in total?

Note: 1. Provide your answer as a whole number.

2. Please make use of the two spreadsheets appeared in previous questions to perform the required calculations. Some of the intermediate results may already be available from earlier questions. However, please make sure that they are correct as they may affect the correctness of your answer to the current question.

Time fo checkout and moving to the staging area (minutes) 7 4 6 5 25 12 2 11 19 Time of picking items Order # (minutes) #1 27 #2 13 #3 10 #4 17 #5 25 #6 12 #7 7 #8 26 #9 37 #10 18 #11 #12 33 14 #14 26 #15 31 #16 23 #17 39 #18 14 #19 60 #20 41 #21 29 19 #23 34 #24 21 #25 36 #13 37 18 19 33 14 26 31 23 14 4 20 11 11 5 9 #22 6 15 Interarrival_times_(minutes) 2.8 6.4 3.5 0.1 1.5 3.3 0.8 7.1 0.8 1.2 0.1 12.8 8.1 3.7 3.6 8.1 4.1 0.7 2.7 5.2 3.3 0.5 0.6 10