Solution
= Solution
For an unramified prime $\mathfrak p$ of $K$ and a prime $\mathfrak P$ of $L$ above it, the Frobenius automorphism is characterized by
$$
\operatorname{Frob}_{\mathfrak P/\mathfrak p}(x)
\equiv x^{N\mathfrak p}\pmod{\mathfrak P}.
$$
In an abelian extension it is independent of $\mathfrak P$. This element is the <Artin symbol>
$$
\left(\frac{L/K}{\mathfrak p}\right).
$$