Z puts on the ace of spades, at Trick 9, as that card and the two trumps in Y's hand make the game. If Z finesses he only scores four, as will be seen by referring to the hands below. Z's play would not be right if he had only five tricks up, as he would then want one more trick to win the game. In that case he should finesse. This is a good illustration of playing to the score.
YZ score three by cards and two by honours.
A'S HAND. | Y'S HAND. | B'S HAND. Kg, 9, 8, 3 ♠|5 ♠|Knv, 10, 4, 2 ♠ Kg, 2 ♡|Ace, Knv, 8, 5, 3 ♡|10, 7, 4 ♡ Kg, 9, 5 ♣|Knv, 6 ♣|Ace, 10, 7, 3 ♣ Ace, Kg, 10, 4 ♢|Qn, 9, 8, 6, 5 ♢|Knv, 2 ♢
At Trick 3, A is justified in risking a force on his partner, though weak in trumps himself. Strength in trumps has been adversely declared by the call (_see_ pp. 132, 133), and there is nothing to show that B has not the queen of diamonds.
At Trick 4, it is doubtful whether A should cover the strengthening card led (_see_ p. 88).
Qn, 9, 7 ♠ Kg, 10, 6, 5 ♡ Qn, 6, 5 ♣ 10, 4, 2 ♢
REMARK (Trick 3).--The knave of diamonds, and therefore the command of trumps, is marked in Y's hand.
REMARK (Trick 7).--Z properly concludes, as his partner has command of trumps (_see_ Remark, Trick 3), that his discard (Trick 6) was from his weakest suit, notwithstanding the adverse trump lead, and therefore Z leads clubs. If Z mistakes the character of his partner's discard, and leads a heart, he loses the game (_see_ pp. 105-6, and apply the rules of play there stated to the present situation).
TRICKS 9 to 13.--Y brings in the clubs (_see_ his hand below), and
A'S HAND. | Y'S HAND. | B'S HAND. Ace, Kg, 10, 2 ♠|6, 4 ♠|Knv, 8, 5, 3 ♠ Ace, 9, 7 ♡|4, 2 ♡|Qn, Knv, 8, 3 ♡ King, 3 ♣|Ace, Knv, 10, 4, 2 ♣|9, 8, 7 ♣ Ace, Kg, Qn, 5 ♢|Knv, 9, 8, 6 ♢|7, 3 ♢
At Trick 7, A is right to cover the queen of clubs (_see_ p. 88).
Getting rid of the command of partner's suit (_see_ p. 97).
Kg, 10, 5 ♠ A, 6, 5 ♡ 9, 8, 3 ♣ 10, 9, 8, 2 ♢
TRICKS 11 to 13.--Z (Trick 11) leads deuce of diamonds. Y makes two tricks in diamonds (note the advantage to YZ of Z's having got rid of the command).
A'S HAND. | Y'S HAND. | B'S HAND. Knv, 9 ♠|8, 7, 6 ♠|Ace, Qn, 4, 3, 2 ♠ Qn, 8 ♡|Knv, 10, 9, 4 ♡|Kg, 7, 3, 2 ♡ Qn, Knv, 10, 6, 5, 4, 2 ♣|Kg ♣|Ace, 7 ♣ 7, 4 ♢|Ace, Qn, Knv, 6, 5 ♢|Kg, 3 ♢