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_8, if x_8 were a poet, then x_8 is sad. For all x_8, if x_8 were sad, then x_8 is a poet. Jessica is sad.
There is at least one x for which x is sad can be inferred via the existential generalization rule. For all x_8, x_8 is a poet if and only if x_8 is sad can be inferred via the universal biconditional introduction rule. For all x_8, x_8 is sad if and only if x_8 is a poet can be inferred via the universal biconditional introduction rule.