Consider the following premises. S(a_10) <-> U(a_10). forall z: U(z) <-> S(z). Can we infer U(a_10) <-> S(a_10) from them?
 From forall z: U(z) <-> S(z) we can infer forall z: U(z) -> S(z). From forall z: U(z) -> S(z) we can infer U(a_10) -> S(a_10). From S(a_10) <-> U(a_10) we can infer S(a_10) -> U(a_10). Finally, from U(a_10) -> S(a_10), S(a_10) -> U(a_10) we can infer U(a_10) <-> S(a_10). Therefore, the answer is yes.