Read the following passage and solve the questions based on it.
(i) Five students S, R, N, M and V have a total of five books on various subjects like—Physics, Chemistry, Mathematics, Biology and English written by authors Gupta, Khanna, Harish, D’Souza and Edgar. Each student has only one book on any one of the five subjects.
(ii) Gupta is the author of the Physics book, which is not owned by V or S.
(iii) M owns the book written by Edgar.
(iv) N owns the Mathematics book. V has the English book which is not written by Khanna. The Biology book is written by D’Souza.
For how many students is it possible to uniquely determine the books owned by them?