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: There is at least one y_1 for which if y_1 were poor, then y_1 is writing a letter. For all y_1, y_1 will write a letter if and only if y_1 is poor.
For all y_1, if y_1 writes a letter, then y_1 is poor can be inferred via the universal biconditional elimination rule. For all y_1, if y_1 were poor, then y_1 is writing a letter can be inferred via the universal biconditional elimination rule.