There are four racks numbered 1, 2, 3, 4 and four books numbered 1, 2, 3, 4. If an even rack has to contain an odd-numbered book and an odd rack contains an even-numbered book, then what is the position of book 4?

I. Second book has been put in third rack.

II. Third book has been put in second rack.

Let's take the two statements individually:

Statement 1: If the second book is in Rack 3, then the fourth book must be in the only remaining odd numbered rack i.e. rack 1. Hence, we can infer the position of book 4 using the first statement.

Statement 2: If the third book is in Rack 2, then the first book must be in Rack 4. However, we don't know anything about the position of Book 4. Hence, we cannot infer the position of book 4 using the second statement.

Hence, the question can be answered using one of the statements but not the other.