Read the following group of sentences. The first and the last sentences are numbered 1 and 6, the rest are numbered P, Q, R, and S. Arrange these four sentences in proper order to form a meaningful paragraph/sentence.

1. Einstein said

P. although more than 900 books had been written

Q. his theory of relativity

R. who understood

S. that there were only twelve people

6. attempting to explain it.