Determine the email and Code of employee who are working at United State, state CA
United States of America refers to country = 'USA'; code of employee refers to employeeNumber;
SELECT T1.email, T1.employeeNumber FROM employees AS T1 INNER JOIN offices AS T2 ON T1.officeCode = T2.officeCode WHERE T2.country = 'USA' AND T2.state = 'CA' GROUP BY T1.email, T1.officeCode