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: If Susan reads a book, then Thomas is not a server. If Jennifer writes a letter, then Thomas is a server. If Linda were sad, then Jennifer is writing a letter. Linda is sad.
Jennifer is writing a letter can be inferred via the modus ponens rule. If Linda were sad, then Thomas is a server can be inferred via the transitivity rule.