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: Mary is reading a book or Linda is playing squash. For all z, z will not write a letter. For all z, z will write a letter if and only if z will read a book.
For all z, if z writes a letter, then z is reading a book can be inferred via the universal biconditional elimination rule. For all z, if z reads a book, then z is writing a letter can be inferred via the universal biconditional elimination rule. For all z, z will not read a book can be inferred via the universal biconditional elimination rule.