noospace wrote:Okay thanks for your help. But I don't see why you're giving me a reference to point out an arithmetic error quite frankly.

It is not an arithmetic error. I made the reference to this book to stimulate you to read carefully the phenomenon and then see clearly why (B) is correct. If the whole matter was an arithmetic error, I would have written the answer, since it is requires a few minutes and a few lines ... . Is that clear? If you read it from a source you will definitely understand what is going on and you will not get confused about this matter in case you see a relative question in the test. The source I mentioned is enough to give you a clear undestanding.

Physics_auth