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_5, if x_5 plays a game, then x_5 is fast. There is at least one x_5 for which x_5 will play a game. For all x_5, x_5 is an office clerk if and only if x_5 is fast.
There is at least one x_5 for which x_5 is fast can be inferred via the existential modus ponens rule. For all x_5, if x_5 were an office clerk, then x_5 is fast can be inferred via the universal biconditional elimination rule. For all x_5, if x_5 were fast, then x_5 is an office clerk can be inferred via the universal biconditional elimination rule.