H1B transfer in premium while Amendment in progress

My original petition filed by my current employer “A” was amended due to location change for which I have also got I 797C (amended petition receipt). Also this amendment I-797C is still showing as “Case Is Received” . In such situation, i have a new employer “B” who is fling up in premium a new petition for h1b transfer. As I have no knowledge of the immigration rules I just wanted to reconfirm with you . Please correct me on my understanding .

B can file for transfer using A’s original approval notice and 797C for the amendment.