Assuming that you generate $15,000$ invoices per month, what recommendation would you give the designer about the use of derived attributes?

SELECT

CUS$\_$CODE, MAX$($LINE$\_$UNITS$*$LINE$\_$PRICE$)$

FROM

CUSTOMER NATURAL JOIN INVOICE NATURAL JOIN LINE

WHERE

CUS$\_$AREACODE $=\text{'}615\text{'}$

GROUP BY

CUS$\_$CODE;