Given the following automaton 

which of the following regular expressions is equivalent to the automata

E_{TM} ={⟨M⟩|M is a TM and L(M)=∅ } is decidable

If one problem is mapping reducible to a second, previously solved problem, we can thereby obtain a solution to the original problem. 

A_{LBA} = {⟨M, w⟩| M is an LBA that accepts string w} is undecidable. 

The decidability of A_{TM} can be proved by contradiction.