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 reads a book, then x_15 is writing a letter. For all x_15, if x_15 writes a letter, then x_15 is reading a book. If Linda writes a letter, then John is climbing a mountain. If John climbs a mountain, then Linda is reading a book.
If Linda writes a letter, then Linda is reading a book. For all x_15, x_15 will read a book if and only if x_15 will write a letter. For all x_15, x_15 will write a letter if and only if x_15 will read a book.