During the normalization process, you end up with the following candidate keys: Key 1: InvoiceNo, Invoice Date Key 2: InvoiceNo, SalespersonlD Key 3: InvoiceNo, SalespersonEmail Key 4: InvoiceNo, SalespersonSSN Assuming each invoice can be handled by more than one salesperson, which pair of the fields would you choose as the Primary Key? Explain the reasons for discarding the options as appropriate: Key 1: Key 2: Key 3: Key 4