A researcher studying organic compounds has found that five different molecules. T, W, X, Y and Z form chains according to the following rules :
A chain consists of three or more molecules, though the molecules in the chain are not necessarily different.
T is never found on either end of a chain. 

If W appears in a chain, it appears more than once.
X is never found next to y in a chain.
W is never found on the end of a chain
unless Z is found somewhere in the chain.
If Y appears in a chain, Z appears also,