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_11, x_11 is a scientist if and only if x_11 will read a book. For all x_11, if x_11 plays a game, then x_11 is a taxi driver. For all x_11, if x_11 were a scientist, then x_11 is not a taxi driver. There is at least one x_11 for which x_11 will play a game.
There is at least one x_11 for which x_11 is a taxi driver can be inferred via the existential modus ponens rule. For all x_11, if x_11 were a scientist, then x_11 is reading a book can be inferred via the universal biconditional elimination rule. For all x_11, if x_11 reads a book, then x_11 is a scientist can be inferred via the universal biconditional elimination rule.