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_15, x_15 will play squash or x_15 will climb a mountain. For all x_15, if x_15 reads a book, then x_15 is not climbing a mountain. For all x_15, x_15 will not play squash. There is at least one x_15 for which x_15 will work if and only if x_15 is bored. For all x_15, x_15 will read a book or x_15 is bored.
For all x_15, x_15 will climb a mountain can be inferred via the universal disjunctive syllogism rule. There is at least one x_15 for which if x_15 works, then x_15 is bored can be inferred via the existential biconditional elimination rule. There is at least one x_15 for which if x_15 were bored, then x_15 is working can be inferred via the existential biconditional elimination rule.