What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all y_4, y_4 will write a letter if and only if y_4 is a lawyer. For all y_4, if y_4 were a mechanic, then y_4 is a musician. There is at least one y_4 for which if y_4 writes a letter, then y_4 is a mechanic.
There is at least one y_4 for which if y_4 writes a letter, then y_4 is a musician. For all y_4, if y_4 writes a letter, then y_4 is a lawyer. For all y_4, if y_4 were a lawyer, then y_4 is writing a letter.