Will I be qualified for the 144 hour transit visa for this itinerary LAX--ICN-PVG-ICN-LAX ?

I've contacted several Los Angeles Chinese Travel agencies but no one knows about this. I will be leaving from LAX , visiting Korea one week, and then going to Shanghai for 4 days, back to Korea for 3 days before coming back to LAX. Will I be qualified for this China 144 hour free transit? I have a US passport. Please Help !!