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: Jessica is a mechanic. If Patricia writes a letter, then Jessica is not a mechanic. Patricia is writing a letter if and only if it is windy.
Patricia is not writing a letter can be inferred via the modus tollens rule. If Patricia writes a letter, then it is windy can be inferred via the biconditional elimination rule. If it is windy, then Patricia is writing a letter can be inferred via the biconditional elimination rule.