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: If William climbs a mountain, then Barbara is playing squash. Patricia is reading a book or Barbara is playing squash. If Barbara plays squash, then William is climbing a mountain. If Patricia reads a book, then William is climbing a mountain.
If Patricia reads a book, then Barbara is playing squash can be inferred via the transitivity rule. William is climbing a mountain can be inferred via the disjunction elimination rule. William is climbing a mountain if and only if Barbara is playing squash can be inferred via the biconditional introduction rule. Barbara is playing squash if and only if William is climbing a mountain can be inferred via the biconditional introduction rule.