Possible Sum can be 4,5,6,7,8,9,10,11 and so on
Turn 1: A SAYS NO, B eliminates unique possibilities,
Sum can't be 4,5,6
Now, sum 7 has 1 possibility (3,4) as (5,2) is ruled out by A
Turn 2: B SAYS NO, A eliminates (3,4)
Product 12 has 2 combo (3,4) and (2,6)
Turn 3: A SAYS NO, (2,6) Eliminated
Sum 8 has 2 combo (2,6) and (4,4)
Turn 4: B SAYS NO, (4,4) Eliminated
Product 16 has 2 combo (4,4) and (2,8)
Since (4,4) is eliminated, A KNOWS IT SHOULD BE 2 AND 8
Now, Sum 10 has 2 combo (2,8) and (6,4)
Since A freezes (2,8), B also finalises (2,8)
ANSWER (2,8)