请教xiaobaitu，pjiang大侠: I-485还未提交就换工作,receive I-485 RFE

My I-140 has approved based company A, then I change job to new employer company B before file I-485.

I file I-485 based on company A's(I-140) during I work in the company B, since the company A still sponsors my GC even if i don't work there.

I received I-485 RFE yesterday from USCIS, asking comapny Verification letter to show job position, salary...

My question: Who should write this letter? From previous company A or the current employer company B??

I really appreciate your guys great help!!!