The last time we sang this Mary Lee had the second sopranos take the Alto 1 part. Since we seem to have more altos and fewer sopranos, she may change that this time. At any rate, whoever sings it, I have labeled it Alto 1 here so it will match the printed score.
The first solo is in the bass track (since it's a bass solo) and the other two are in the tenor 1 track. I have no idea who will actually sing them but that's where you can find them.
To play the track, just click on the line you want to listen to. You can fast forward and rewind through the track by dragging the little moving line. To pause playback, click on the pause sign on the album cover.