“…This is easily checked directly, and is a special case of [AJ12, Proposition 5.2], which proves a generalization to higher-dimensional local fields; see also [Lau88], where the analogous result is proved for general APF extensions (strictly speaking, the result of [Lau88] does not apply as written in our situation, as the extension is not Galois; but, in fact, the argument still works). In brief, it is enough to check separately the cases that is either unramified or totally ramified; in the former case the result is immediate, while the latter case follows from Dwork’s description of Artin’s reciprocity map for totally ramified abelian extensions [Ser79, XIII §5 Corollary to Theorem 2].◻…”