ASA Question

[IRISHMAFIA]

With two outs, R1 on 3B and R2 on 1B, B5 hits a ball that deflects off of F6's glove. B5 is obstructed rounding 1B and the base umpire signals obstruction. Prior to R2 reaching home plate, B5 is tagged out during a rundown going back to 1B. The plate umpire should:

a) signal that R2's run does not count.
b) hesitate to see if the base umpire enforces obstruction.
c) after play is completed, call "Dead Ball", confer with the base umpire, then rule if R2's run counts.
d) none of the above.

a) If the PU did not see the DDB signal, this would be correct
b) If the PU did see the DDB signal, this would be correct
c) If the PU did not see the DDB signal, why would he rule "Dead Ball". If he did see the DDB signal, that really isn't his call, though it would be correct in this situation.
d) I would have an easier time if it said "all of the above".

Thoughts?