2. Whether A's patent right is infringing must first determine whether A's patent right is stable, and any invention granted with patent right may be invalid. If A's patent right is stable and cannot be invalidated, it will violate A's patent right. If A's patent right is unstable, it can be invalid without infringing A's patent right. (Being invalidated means that the patent right is not considered to exist from beginning to end. )
3. If A's patent right is stable, then A should pay royalties to its patentee; If the patent right of A is unstable, there is no need to pay the patent fee.