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: There is at least one x for which x will write a letter. For all x, x is sad.
There is at least one x for which x will write a letter and x is sad can be inferred via the existential conjunction rule. There is at least one x for which x is sad and x will write a letter can be inferred via the existential conjunction rule.