What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all x_15, if x_15 drinks water, then x_15 is an artist. David is an artist if and only if William is writing a letter. David is driving a car if and only if David is drinking water. William is not writing a letter.
If David were an artist, then William is writing a letter. If David drives a car, then David is drinking water. If William writes a letter, then David is an artist. If David drinks water, then David is driving a car. David is not an artist.