It's easy! :) When solving double dummy problems you cannot consider mistakes, as other answers to this post suggest. N cannot take 9 tricks on accurate defense. And that would be, taking in consideration all possible ways that this board could unfold, the following: First of all the lead has to be ♥K or ♥J 1) If N takes the first round and: a) play clubs right away he will make 1♥ + 5♦ + 1♣ = 7 tricks and when he will try to establish his 2nd spade trick E would have an entry with his other heart honor to cash the good clubs; b) crosses with ♦A to dummy to play the ♠Q in order to establish the spade trick first, W will cover, N wins with A and plays ♠10(else is similar to 1.a)); now, W takes his ♠J and continues spade, setting up the suit with ♥Q as an entry when E wins the first round of clubs with the A; 2) If N ducks first trick, E continues with ♥7, now: a) N tries to first establish the club trick, E takes the first round of clubs and unblocks ♥K in order to set up his partner ♥Q to be cashed when getting in with the ♠J. In this case the declarer is hold to 1♠ + 1♥ + 5♦ + 1♣ = 8 tricks. b) N crosses to dummy with ♦A in order to set up a 2nd spade trick, W covers the ♠Q and ducks! the ♠10 in order to preserve the defense communication...now declarer can make 2♠ + 1♥ + 5♦ = 8 tricks and when tries the finesse in clubs, E takes his A and cashes his ♥K and exits his well preserved spade in order to cross to W fot him to cash his ♥Q as well, for the defense to take 1♠ + 3♥ + 1♣ = -1 3) Declarer tries to break the defense communication by taking the first trick and continues with a heart, now E has to play small in order to let his partner in with the ♥Q, now W will have to play his stiff ♣Q, E overtakes with the A and continues with a high club in order to set 2 more club triks, having his other heart honor serving as entry to the clubs. Defense takes 3♣ + 2♥ (+1♠ if declarer tries to set up a spade trick instead of cashing his 8 tricks) This lead could be made on proper information from the bidding(I cannot comment on that since there is no bidding attached) and very good understanding of the game. After the mandatory lead, the defense could prevail with good logic, precise counting and figuring out how they can take 5 before declarer takes 9(a bit more complex than intermediare bridge skills, but not that out of reach). I would say that the play on trick 2 would be crucial(considering the optimal lead and the duck from declarer), if first 2 tricks go well for the defense the contract will probably go down.
