Let \( G \) be a simple, unweighted, and undirected graph. A subset of the vertices and edges of \( G \) are shown below.
It is given that \( a - b - c - d \) is a shortest path between \( a \) and \( d \); \( e - f - g - h \) is a shortest path between \( e \) and \( h \); \( a - f - c - h \) is a shortest path between \( a \) and \( h \). Which of the following is/are NOT the edges of \( G \)?
The surface integral \( \int_S x^2 \, dS \) over the upper hemisphere
\[ z = \sqrt{1 - x^2 - y^2} \]
with radius 1 is ..........