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: For all x_7, x_7 is sad if and only if x_7 is fast. If Sarah were fast, then Jessica is a musician. Jessica is a musician if and only if Elisabeth is reading a book. Elisabeth is not reading a book.
If Jessica were a musician, then Elisabeth is reading a book can be inferred via the biconditional elimination rule. If Elisabeth reads a book, then Jessica is a musician can be inferred via the biconditional elimination rule. Jessica is not a musician can be inferred via the biconditional elimination rule. For all x_7, if x_7 were sad, then x_7 is fast can be inferred via the universal biconditional elimination rule. For all x_7, if x_7 were fast, then x_7 is sad can be inferred via the universal biconditional elimination rule.