set of CR's

At an evening concert, a total of six songs—O, P, T, X, Y, and
Z—will be performed by three vocalists—George, Helen, and
Leslie. The songswill be sung consecutively as solos, and
each will be performed exactly once. The following
constraints govern the composition of the concert program:
Ymust be performed earlier than T and earlier than O.
P must be performed earlier than Z and later than O.
George can perform only X, Y, and Z.
Helen can perform only T, P, and X.
Leslie can perform only O, P, and X.
The vocalistwhoperforms firstmust bedifferent fromthe
vocalist who performs last.
19. Which one of the following is an acceptable schedule for
the performance of the songs, in order from the first to
last song performed?
(A) X, T, Y, O, P, Z
(B) X, Z, Y, T, O, P
(C) Y, O, P, X, T, Z
(D) Y, P, O, Z, T, X
(E) Y, X, O, P, Z, T
20. Which one of the following must be true about the
program?
(A) George performs X.
(B) Helen performs O.
(C) Helen performs T.
(D) Leslie performs P.
(E) Leslie performs X.
21. Which one of the following is a complete and accurate
list of the songs any one of which could be the last song
performed at the concert?
(A) O, P, Z
(B) O, T, X
(C) T, P, Z
(D) T, X, Z
(E) X, P, Z
22. If X is performed first, which one of the
following must be true?
(A) X is performed by George.
(B) X is performed by Helen.
(C) P is the fourth song performed.
(D) Y is the second song performed.
(E) Y is the third song performed.
23. Each of the following is an acceptable schedule for the
performance of the songs, in order fromthe first to last
song performed, EXCEPT:
(A) Y, O, P, T, Z, X
(B) Y, T, O, P, X, Z
(C) Y, X, O, P, Z, T
(D) X, Y, O, P, Z, T
(E) X, Y, O, T, P, Z
24. If Y is performed first, the songs performed second,
third, and fourth, respectively, could be
(A) T, X, andO
(B) T, Z, andO
(C) X, O, and P
(D) X, P, and Z
(E) X, T, andO