Consider the following premises. u <-> t. forall x_10: ~R_10(x_10). R_10(a_10) <-> u. Can we infer t from them? If possible, name the inference rules being used at each step.
 From forall x_10: ~R_10(x_10) we can infer ~R_10(a_10) via universal instantiation. From R_10(a_10) <-> u, ~R_10(a_10) we can infer ~u via biconditional elimination. Finally, from u <-> t, ~u we can infer ~t via biconditional elimination, which contradicts t. Therefore, the answer is no.