How to stop mail for previous residents<br>Write " return to sender " on the exterior of the envelope. Then place the mail in an outgoing mailbox. This notifies the post office and the original sender that the recipient no longer lives at that address.

Choose your answer: based on the paragraph above can we conclude that "it will take a week for it to go into effect"?

OPTIONS:
 a). Yes;
 b). It's impossible to say;
 c). No;
I think the answer is
b).