Situation: runners on 2nd and 3rd (R3 & R2 respectively). 2 man crew. U1 in C position. F5 playing even with the 3rd base bag. Batter hits a low sinking line drive directly at F5 who takes a step forward towards home plate and short hops/traps the ball. Knowing that a prompt call is needed in this situation to eliminate any confusion, which umpire (PU or U1) is responsible for the "catch or no catch?". Obviously we don't want conflicting calls.