I am trying to figure out how Transtutors came to a solution in part B of one of the textbook…

I am trying to figure out how Transtutors came to a solution in part B of one of the textbook…

I am trying to figure out how Transtutors came to a solution in part B of one of the textbook questions. It needs a little more explaining. When I click the “offer feedback” option it does not allow me to submit feedback.. just trying to figure this problem out been on it a long time!
Here is a link to the chapter questions of the book
https://books.google.com/books?id=8kDuAwAAQBAJ&pg=PA581&lpg=PA581&dq=the+loebuck+grocery+must+decide+how+many+cases+of&source=bl&ots=5rWXF5Jcd7&sig=ioVreTuMUT_Oj7n_e0NULASohrM&hl=en&sa=X&ei=tjqzVNn5KceZgwSz0YO4CQ&ved=0CBwQ6AEwAQ#v=onepage&q=the%20loebuck%20grocery%20must%20decide%20how%20many%20cases%20of&f=false
http://www.Transtutors.com/homework-help/introduction-to-management-science-11th-edition-chapter-13-problem-14p-solution-9780132751919
is the question/answer
1. how does the question get U as 40? they get 9.3 because 28 divide by 3? 2. also according to google time clock 0.008 hours is not 45 seconds. 3. Also, is it 3 more assistants making it 4 total? or two more making it 3 total? two more is bolded at the top then three more is bolded at the end… its step 2 of 2 “in order to get the wait time down etc etc”… thank you!