A jazz group plans to play six pieces - J, K, L, M, N and O - during a set . Each piece will be played exactly thrice. The order in which the pieces are to be played is subject to the following conditions:
N must be played before J and before O.
M must be played later than J.
K must be the third Piece.
If the group plays L sixth, which of the following could be the first and second pieces of the set, respectively ?
I. N and J
II. N and O
III. J and O

Options

A. I only
B. II only
C. I and II only
D. I and III only

Answer

C

Explanation

Begin by summarising the information: `Nlt(J+O)`
`JltM`
K = 3
There is one further conclusion that can be drawn. Since N is to be played before J and J before M, N must be played before M.
Enter the additional information in a diagram:
`{:("1 2 3 4 5 6"),(" K L "):}`
Since N must be played before J, O, and M, N must be first :
`{:("1 2 3 4 5 6"),("N K L "):}`
Now, given that J must precede M, there are only three possibilities :

So, the first and second pieces could be N and J, or N and O.