Consider the following premises. For all x_12, x_12 is fast if and only if x_12 is a poet. For all x_12, x_12 will read a book. For all x_12, if x_12 reads a book, then x_12 is a poet. Can we infer the following from them? If we can, name the inference rule being used: For all x_12, x_12 is fast or x_12 is a musician.
 From the fact that for all x_12, x_12 is fast if and only if x_12 is a poet we can infer that for all x_12, if x_12 were a poet, then x_12 is fast via universal biconditional elimination. From the fact that for all x_12, if x_12 reads a book, then x_12 is a poet, and that for all x_12, x_12 will read a book we can infer that for all x_12, x_12 is a poet via universal modus ponens. From the fact that for all x_12, if x_12 were a poet, then x_12 is fast, and that for all x_12, x_12 is a poet we can infer that for all x_12, x_12 is fast via universal modus ponens. Finally, from the fact that for all x_12, x_12 is fast we can infer that for all x_12, x_12 is fast or x_12 is a musician via universal addition. Therefore, the answer is yes.