20 tills no more than 4 customer per till

Hi all,

Right.. I have been given an A-level ICT task to complete which involves producing an answer that will later be placed into an excel spreadsheet. Basically the question I have is as follows: "if a supermarket has **20 tills**, how would I work out the **minimum number** of tills needed open **per hour**, if a maximum of **4 customers are allowed to be queuing at 1 till at a time**". I know the following figures:

- The average staff member can scan 1552 items per hour.
- The average customer purchases 60 items per hour.
- There are 147 customers per hour.

so is anybody can use those figures to determine the number of tills which need to be open with no more than 4 customer per till at any 1 time. Any help will be great, especially if you can post the steps you took to get to the final result.

Thanks in advance,

Tom