There are 6 physics books and 1 chemistry book on shelf P and 4 physics books on shelf Q. One book is moved from shelf P to shelf Q. A student picks up a book from shelf Q. What is the probability that the chemistry book is taken by the student?  Choose the correct answer.
A) 1/42
B) 1/35
C) 1/28
D) 1/21
E) 1/14
P(a chemistry book is moved to shelf Q) = 1/7   P(a chemistry book is then chosen from shelf Q) = 1/5   P(the student takes a chemistry book) = 1/7 * 1/5 = 1/35   The answer is 1/35.
<result>B</result>
There are 6 physics books and 1 chemistry book on shelf P and 4 physics books on shelf Q. One book is moved from shelf P to shelf Q. A student picks up a book from shelf Q. What is the probability that the chemistry book is taken by the student?