Every problem X in NP can be reduced in polynomial time to SAT by encoding the computation of the accepting nondeterministic Turing machine for X as a propositional formula

Similarly, parts i) and ii) respectively implies that \(\textbf{P} \subsetneq \textbf{EXP}\) and \(\textbf{NP} \subsetneq \textbf{NEXP}\). And it similarly follows from part iii) that \(\textbf{L} \subsetneq \textbf{PSPACE}\). Note that since every deterministic Turing machine is, by definition, a non-deterministic machine, we clearly have \(\textbf{P} \subseteq \textbf{NP}\) and \(\textbf{PSPACE} \subseteq \textbf{NPSPACE}\). 2 Suppose that \(f(n)\) is both time and space constructible. Then