Read the following scenario and address the following issues that are related to transaction and concurrency control.

Assume that objects a1, a2, and a3 are managed by a server, which provides two operations to operate the objects.

read(a): returns the value of object a

write(a, v): assigns the value v to object a

Assume that the following two concurrent transactions T and U are performed on these objects

T: read(a2); read(a1); write(a2, a2-25); read(a3); write(a1, a1+52)

U: read(a3); read(a2); write(a2, a2+33); write(a3, a3-26)

Assume that the original values of a1, a2, and a3 are 111, 106 and 125 respectively. Answer the following questions based on the above scenario.

---> We rearrange Ts operations as follows and keep Us operations unchanged.

T: read(a2); read(a1); read (a3); write(a2, a2-25); write(a1, a1+52)

If we use the locks as below, what problem would happen?

Time Sequence Transactions T: lock a2: T: read(a2) T: lock a 1; T: read(a1); T: wait for the lock of a3; U:lock a3; U: read(a3) U: wait for the lock of a2; U: wait for the lock of a2; Time Sequence Transactions T: lock a2: T: read(a2) T: lock a 1; T: read(a1); T: wait for the lock of a3; U:lock a3; U: read(a3) U: wait for the lock of a2; U: wait for the lock of a2