If :
A # B means B is the mother of A ;
A $ B means A is the father of B ;
A % B means A is the sister of B ;
A * B means A is the son of B ;
A @ B means A is the brother of B ;
A ! B means A is the daughter of B
Then determine that if:
P $ Q # R % S
Then, how is R related to P ?

A

sister

B

son

C

niece

D

wife

E

mother