I need only part (b) of this question. So please solve only part (b).

6. (a) Prove that the family of context-free languages is not closed under difference in general,

but it is closed under regular difference, that is, if L1 is context-free and L2 is regular, then

L1 1 L2 is context-free.

(b) Show that the family of deterministic context-free languages is not closed under union and

intersection.