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 it is sunny, then Susan is a musician. If Susan were a musician, then it is sunny. If it is sunny, then Susan is a musician.
It is sunny if and only if Susan is a musician can be inferred via the biconditional introduction rule. Susan is a musician if and only if it is sunny can be inferred via the biconditional introduction rule. Susan is a musician if and only if it is sunny can be inferred via the biconditional introduction rule. It is sunny if and only if Susan is a musician can be inferred via the biconditional introduction rule.