$1.$ Consider the following SQL code that updates $3$ tables and answer A & B:

BEGIN TRANSACTION$$ Start transaction

$$

INSERT INTO INVOICE$$ Add record to invoice

$($INV$\_$NUM, INV$\_$DATE, ACCNUM, TOTAL$)$

VALUES $(1020,\text{'}15-$MAR$-2018\text{'},\text{'}60120010\text{'},3500)$;

$$

UPDATE INVENTRY$$ Update the quantity on hand of the

SET ON$\_$HAND $=$ ON$\_$HAND $100$ product

WHERE PROD$\_$CODE $=\text{'}345$TYX$\text{'}$;

$$

UPDATE ACCREC$$ Update the customer balance

SET BALANCE $=$ BALANCE $+3500$ account

WHERE ACCNUM $=\text{'}60120010\text{'}$;

$$

COMMIT;

A$.$ How would you change the code to achieve Pessimistic but Not $2-$Phase Locking?

B$.$ How would you change the code to achieve Pessimistic $2-$Phase Locking protocol?