回复：突发奇想，不知道是否可行，烦请各位大侠指点

1. PD retention takes effect only after 140 is approved. So you cann't do that unless a 140 based on A's LC is approved.
2. Even a 140 based on A's LC was once approved, the 140 must be still alive (not revoked or withdrawn )in order for you to use its PD.