In a certain code language,
'A + B' means 'A is the brother of B',
'A - B' means 'A is the mother of B',
'A × B' means 'A is the father of B' and
'A ÷ B' means 'A is the son of B'.
If P × Q × R + D ÷ S - B, then which of the following statements is NOT correct?
1
R is B's brother.
2
Q is B's father.
3
P is B's mother's father.
4
R is P's son's son.