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, x_7 is sad if and only if x_7 will play tennis. For all x_7, x_7 will work if and only if x_7 is sad. There is at least one x_7 for which if x_7 were an office clerk, then x_7 is playing tennis. For all x_7, x_7 will not work.
For all x_7, if x_7 were sad, then x_7 is playing tennis can be inferred via the universal biconditional elimination rule. For all x_7, if x_7 works, then x_7 is sad can be inferred via the universal biconditional elimination rule. For all x_7, if x_7 plays tennis, then x_7 is sad can be inferred via the universal biconditional elimination rule. For all x_7, if x_7 were sad, then x_7 is working can be inferred via the universal biconditional elimination rule. For all x_7, x_7 is not sad can be inferred via the universal biconditional elimination rule.