^Queues
~Given the following queue operations...

    push (16)
    push (20)
    push (19)
    pop  (x)
    push (18)
    push (17)
    pop  (y)
    pop  (z)
    pop  (z)

... what are the contents of x,y and z, after the operations have been
performed?

a.  x = 16, y = 20, z = 18
b.  x = 16, y = 17, z = 19
c.  x = 20, y = 17, z = 18
d.  x = 19, y = 16, z = 20
e.  x = 16, y = 19, z = 18