Is the language Sol decidable or not?


I define the language Sol as a turing machine M with alphabet{s,o,l} and we want to decide if sol $ \in$ L(M).

Is this decidable? How can I prove it? It seems that three case could occur either sol $ \in L(M)$ or sol $ \notin$ L(M) or the Turing machine M would loop. Is trying to use mapping reducibility with the language $ A_{TM}$ defined as a Tm M that accepts w a good idea? If possible this would prove that Sol is undecidable because $ A_{TM}$ undecidable.