Proposition 10

Let $\mathfrak{a}$ and $\mathfrak{b}$ be cardinals and let I be a set such that $\mathrm{Card}\ (I) = \mathfrak{b}$. If $\mathfrak{a}_{\iota} = \mathfrak{a}$ for all $\iota \in I$, we have $\mathfrak{a}^{\mathfrak{b}} = \mathbf{P}_{\iota \in I} \mathfrak{a}_{\iota}$.

This follows from the definition of the product of a family of sets as a set of functional graphs (Chapter II, § 5, no. 3).