Sunlight

[SRW]

Runners on base, doesn't matter where. Outs don't matter. Sun is setting directly down the left field line. One-umpire mechanic slow pitch game. You're it.

Batter hits a shot down the left field line.

Due to the sun, you lose sight of the ball. You have no clue whether the ball landed a foot fair or a foot foul... but it's real close. One team's yelling "fair" while the other's yelling "foul". When you can finally see anything, you see F7 picking up the ball off the ground about 4 feet foul.

What do you do?