Suppose that we want to expand our database and want to collect and store info regarding customer birthday so we can send out promotion, which method below would best be used to achieve that?

a. Insert a new field called "Date of Birth" into the Retailer_Sales table
b. Insert a new field called "Date of Birth" into the Retailer_Customers
c. Both of the methods above should work
d. We cannot do this because the relational database would not allow use to do so