What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? For all x_13, x_13 will read a book if and only if x_13 is sad. There is at least one x_13 for which x_13 is sad. For all x_13, x_13 will play tennis.
There is at least one x_13 for which x_13 is sad and x_13 will play tennis. There is at least one x_13 for which x_13 will play tennis and x_13 is sad. For all x_13, if x_13 reads a book, then x_13 is sad. For all x_13, if x_13 were sad, then x_13 is reading a book.