What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: For all y, y will not write a letter. For all y, y will write a letter or y is not a mechanic. There is at least one y for which if y writes a letter, then y is a mechanic.
For all y, if y were a mechanic, then y is writing a letter can be inferred via the universal rewriting rule.