A Mathematical Bridge Problem

Playing a spade contract, you reach trick 10 in your hand to see the following four card configurations:

Dummy holds: ♠ - ♥ AQJ ♦ - ♣ A
You hold: ♠ 2 ♥ 2 ♦ 2 ♣ 2

How do you play to maximize your chance of getting all of the last four tricks? Assume that the only point card left is the king of hearts and there is a diamond higher than the 2 in one of the opponents' hands.

Obviously it depends on your situation, so say that the following happened: your partnership started with 21 high card points between you and during play LHO has played 16 points and RHO has played none. Does this change your answer? What are the probabilities now?

Does your answers change depending on which of the following situations happened?

• Neither opponent bid during the auction
• LHO opened an artificial 1♣ showing 16+ points
• LHO opened a standard bid showing 13-21 points. Does it matter what bid it was?
  

I'm not sure of the answer to this question, so I'm interested to see what the readers of my blog think.