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: For all x_7, if x_7 plays squash, then x_7 is writing a letter. For all x_7, if x_7 writes a letter, then x_7 is playing squash. For all x_7, if x_7 were an artist, then x_7 is playing squash. For all x_7, x_7 will write a letter.
For all x_7, x_7 will play squash can be inferred via the universal modus ponens rule. For all x_7, if x_7 were an artist, then x_7 is writing a letter can be inferred via the universal transitivity rule. For all x_7, x_7 will play squash if and only if x_7 will write a letter can be inferred via the universal biconditional introduction rule. For all x_7, x_7 will write a letter if and only if x_7 will play squash can be inferred via the universal biconditional introduction rule.