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: Sarah is driving a car. Patricia is fast if and only if Richard is a doctor. Richard is a doctor if and only if it is sunny. It is not sunny.
Sarah is driving a car and it is not sunny can be inferred via the conjunction rule. It is not sunny and Sarah is driving a car can be inferred via the conjunction rule. If Patricia were fast, then Richard is a doctor can be inferred via the biconditional elimination rule. If Richard were a doctor, then it is sunny can be inferred via the biconditional elimination rule. If Richard were a doctor, then Patricia is fast can be inferred via the biconditional elimination rule. If it is sunny, then Richard is a doctor can be inferred via the biconditional elimination rule. Richard is not a doctor can be inferred via the biconditional elimination rule.