A spherical wooden ball of radius r is to be divided into eight identical parts by cutting by planes passing through the same diameter. What is the surface area of each final piece?
1
\(\frac{\pi r^2}{3}\)
2
\(\frac{3 \pi r^2}{2}\)
3
\(\frac{2 \pi r^2}{3}\)
4
\(\frac{4 \pi r^2}{3}\)