A Fairly Weak Suit
North/South can make 10 tricks in notrump or spades, or 11 tricks in diamonds, but their best score is in hearts, where they can make 11 tricks.
The defense needs to lead trumps to cut down on spade ruffs. North wins the heart ace and leads a club, East forced to split his honors.
South wins the ace, plays the ace and king of diamonds, ruffs a diamond in North, leads a club, finessing East's remaining honor, then takes the remaining club winner to this position:
South plays a last club, and North ruffs with the heart nine, East unable to overruff. Now North cashes the ♠ A
and ruffs a spade with the ♥ 7
. Finally, South leads a diamond at this position:
North scores his fifth trump trick on top of a spade, three clubs, and two diamonds.