H1B extension after 6 years and changing employers

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Hi,

I have I-140 approved from my current employer and my H1B expires on Oct 30 2017 (roughly 8 months from now). I am planning to change employers now, what are options for me?
1) New employer files for Perm in say 2 months, can they file for my H1B extension for 3 years using my already approved I40 from my current employer?
or
2) New employer will have to file Perm, then file for extension for H1B for 1 year (since no I140 approved from new employer), wait for Perm & I40 from new employer and then file for H1B for 3 years after that?

Plz help, I wnna make a decision regarding changing employers soon.

Thanks,
Deepa