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: Patricia is reading a book if and only if Linda is sad. Linda is not sad. If Karen sleeps, then Patricia is a scientist. If Patricia reads a book, then Patricia is a scientist. For all x_21, if x_21 were a scientist, then x_21 is reading a book.
If Patricia reads a book, then Linda is sad can be inferred via the biconditional elimination rule. If Linda were sad, then Patricia is reading a book can be inferred via the biconditional elimination rule. Patricia is not reading a book can be inferred via the biconditional elimination rule.