Consider table Product(Item,Price) where Item is a key, and the following two concurrent transactions.

T1:

Begin Transaction

update Product set Price = 2*Price where Item = Laptop;

insert into Product values (Printer,$100);

Commit;

T2:

Begin Transaction

select max(Price) as a1 from Product;

select max(Price) as a2 from Product;

Commit;

Assume that the individual statements in a given transaction always execute atomically. Suppose initially there are two tuples in Item: (Laptop, 1000), (PC,900). Each transaction runs once and commits. Transaction T1 always executes with isolation level Serializable.

(a) If transaction T2 executes with isolation level Read-Uncommitted, what possible pairs of values a1 and a2 are returned by T2.

(b If transaction T2 executes with isolation level Read-Committed, what possible pairs of values a1 and a2 are returned by T2.

(c) If transaction T2 executes with isolation level Repeatable-Read, what possible pairs of values a1 and a2 are returned by T2.

(d) If transaction T2 executes with isolation level Serializable, what possible pairs of values a1 and a2 are returned by T2.