Read the following information carefully and answer the questions which follow.
(i) ′A×B′ means 'A is the son of B'.
(ii) ′A+B′ means 'A is the daughter of B'.
(iii) ′A+B′ means 'A is the wife of B'.
(iv) ′A−B′ means 'A is the father of B'.
What will come in the place of the question mark (?) to establish that Q is the mother of N in the expression ′N+O−P?Q′?