Separate Audio File in Layer B; Trying to extend layer A to match it

Hello,

I recorded a screen video, and I have that on layer A. I recorded separate audio and added that to layer B. The audio plays a few seconds longer than the video, so I would like layer A to extend on the last frame of the video so it matches the length of layer B. Otherwise, the audio plays and there's a black screen for the last few seconds. Taking time out of the audio file isn't an option because it's timed to the screen video, until that last few seconds when I complete a thought after the last action on the screen video is done.

Any insight into how I might accomplish this?

Thanks.