Average weekly sales

Thank you Ashish_Mathur! While this works for the single product "A" that I've supplied in the sample data, I'm not able to replicate the same results once I apply this logic to my entire data set.  I have thousands of products that are divided out into different product categories.  When I attempt to add a second product "B", I get this error: 

Data
Column 'Date' in Table 'Data' contains a duplicate value '1/3/2015' and 
this is not allowed for columns on the one side of a many-to-one 
relationship or for columns that are used as the primary key of a table.  

Once everything is working properly, I ultimately will need to be able to use slicers to pick different individual products, or view total categories of products.  I hope this helps.