Total number of acyclic structural isomers possible with the formula, C4H8 is ‘X’. Total number of structurally isomeric terminal alkenes possible with the formula, C4H8 is ‘Y’. Difference between X and Y is

(1), (2), (3)--cis and trans….4 acyclic isomers….. 3 structural , 2 stereo;(4), (5)--------- ---------------------------------two cyclic isomers…both structural ;(1), (2), (3)--cis and trans, (4), (5)…..total six isomers ;