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_11 for which x_11 will not drink water. For all x_11, x_11 will write a letter or x_11 is an office clerk. For all x_11, if x_11 writes a letter, then x_11 is drinking water.
There is at least one x_11 for which x_11 will not write a letter can be inferred via the existential modus tollens rule.