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Kirsten Cookie Case

Solution to Kristen's Cookie Company (A)

Before answering specific questions, it is useful to make a diagram of the overall process:
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Note that in this diagram, activities are arranged in columns to indicate which resources are being used. Inside each activity symbol are written the capacity (in dozens of cookies) and the cycle time (in minutes).
1. How long will it take for you to fill a rush order?
Assuming this order is for one dozen cookies, we will need to do the following:
|Activity |Resource |Cycle Time |Start Time |Finish Time |
|Order Entry |E-mail |0 minutes |00:00 |00:00 |
|Wash Bowl, Mix |Self |6 minutes |00:00 |06:00 |
|Fill Tray |Self |2 minutes |06:00 |08:00 |
|Prepare Oven |Roommate |1 minute |08:00 |09:00 |
|Bake |Oven |9 minutes |09:00 |18:00 |
|Remove |Roommate |0 minutes |18:00 |18:00 |
|Cool |None |5 minutes |18:00 |23:00 |
|Pack, Collect Money |Roommate |3 minutes |23:00 |26:00 |

Therefore, the minimum time to fill an order is 26 minutes. We can illustrate the sequence of events with a Gantt chart:
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2. How many orders can you fill in a night, assuming you are open four hours each night?
Here is a Gantt chart for two batches of one dozen cookies each. It doesn't take twice as long to produce two batches as it does to produce one batch, because you can start mixing the second batch without having to wait for the whole first-batch process...