This is formula which I must write as CNF, DNF and Negation of formula as CNF and DNF: $$(p \rightarrow (q \rightarrow r)) \rightarrow ((p \rightarrow \neg r) \rightarrow (p \rightarrow \neg q))$$
After I get rid of the implications I got something like this (DNF FORM): $$(p \wedge q \wedge r) \vee (p \wedge \neg r) \vee \neg p \vee \neg q$$
And this is the answer in my book, but what's the difference between a good answer and Wolfram's?
One more question. How can i turn it to CNF ?