where to file petition

[arunbn]

I am finishing up my 6years of h1 and going to file for 3 yr extension based on AC21 I140 approval. My normal jurisdiction is the vermont office but in the instructions it says employers exempt from cap need to send to california. My employer is not cap-exempt but my petition is cap-exempt because of AC21 portability so where do I apply to?

Also in the h1b data collection supplement, I marked I am exempt from the cap(Section C) because the petition is for 7th year extension under AC21 portability. Is that what I should check or should I just check extension of stay?