Math 121 intro to statistics


I am going to go crazy! I need a few hints on this one. I am sure this is a trick question testing my logic as well as knowledge of relative frequency histograms. I have some confidence in building the histogram and the math of making it relative. Still I am stuck on what is the actual frequency in this question. Is it number of weeks, number of units? I tried constructing a leaf and stem first but I am so confused. I know the total units is 311, which will help me determine relative frequency (I think). A hint please! What is f in this problem? What data am I using across x axis (is it weeks). Don’t give me the answers to the questions, I have that. I need to know how to arrive at the answers. And now the question:

in a particular kitchen appliance store, the weekly sales of an electric automatic rice cooker for the last 20 weeks are as follows.

20 15 14 14 18
15 17 16 16 18

15 19 12 13 09
19 15 15 16 15

In retail sales, too large an inventory ties up capital, while too small an inventory costs lost sales and customer satisfaction. Using the relative frequency histogram for these data, find approximately how many rice cookers must be in stock at the beginning of each week if:
1.the store is not to run out of stock by the end of a week for more than 15% of the weeks; and
2. the store is not to run out of stock by the end of a week for more than 5% of the weeks.