What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? There is at least one x_9 for which x_9 will write a letter. For all x_9, if x_9 were a mechanic, then x_9 is not writing a letter. For all x_9, if x_9 were a musician, then x_9 is a mechanic. For all x_9, if x_9 were a mechanic, then x_9 is a musician.
There is at least one x_9 for which x_9 is not a mechanic. For all x_9, x_9 is a musician if and only if x_9 is a mechanic. For all x_9, x_9 is a mechanic if and only if x_9 is a musician.