What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? If John were a mechanic, then Barbara is drinking water. If Susan were curious, then Barbara is drinking water. If Barbara drinks water, then John is a mechanic.
If Susan were curious, then John is a mechanic. John is a mechanic if and only if Barbara is drinking water. Barbara is drinking water if and only if John is a mechanic.