AC21 law - Employer Letter

[yourfriend2]

Hi Everybody

I have following questions related to AC21 law:

I have changed the employer after my I485 is filed but working in the SAME position with the SAME client.

When do my new employer need to send a letter to INS stating the change of employer.

(a) immediately
or
(b) Wait for an RFE (Request for Evidence) from the INS.

How will the INS know about the change in employment until my new employer notify?

Please help..

Thank you.