What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Jessica is writing a letter if and only if Jessica is a poet. If Sarah were a cashier, then Jessica is writing a letter. Jessica is a poet if and only if David is a politician. David is not a politician.
If Jessica writes a letter, then Jessica is a poet. If Jessica were a poet, then David is a politician. If Jessica were a poet, then Jessica is writing a letter. If David were a politician, then Jessica is a poet. Jessica is not a poet.