The vector surface integral \(\iint_{\mathcal{S}} \mathbf{F} \cdot d \mathbf{S}\) is equal to the scalar surface integral of the function (choose the correct answer):
(a) \(\|\mathbf{F}\|\).
(b) \(\mathbf{F} \cdot \mathbf{N}\), where \(\mathbf{N}\) is a normal vector.
(c) \(\mathbf{F} \cdot \mathbf{n}\), where \(\mathbf{n}\) is the unit normal vector.