Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE Invoices ( Order_Quantity INTEGER, payment_method_code VARCHAR )

### Question ###
What is the average quantities ordered with payment method code 'MasterCard' on invoices?

### Accurate SQL ###

SELECT AVG(Order_Quantity) FROM Invoices WHERE payment_method_code = "MasterCard"