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 an astronaut. Joseph is an artist if and only if it is sunny. If Jessica were an astronaut, then Linda is writing a letter. If it is sunny, then Linda is not writing a letter.
Linda is writing a letter can be inferred via the modus ponens rule. If Joseph were an artist, then it is sunny can be inferred via the biconditional elimination rule. If it is sunny, then Joseph is an artist can be inferred via the biconditional elimination rule.