= Solution
{c}
For the electron-doped sample, sketch six closed ellipsoids centred on the $\Gamma$--X axes, just inside the six square faces of the face-centred-cubic <first Brillouin zone>, with long axes pointing radially toward X. In the parabolic approximation,
$$
\frac{\delta k_\perp^2}{2m_1(\mu-E_c)/\hbar^2}+\frac{\delta k_\parallel^2}{2m_2(\mu-E_c)/\hbar^2}=1.
$$
The radial-to-transverse semiaxis ratio is $\sqrt{m_2/m_1}\simeq2.2$. The readable conduction minimum near X and its crossing of $\mu$ support these electron <Fermi surface> pockets. The two $[001]$ <cyclotron resonance> fields arise from the two distinct orientations of the six ellipsoids, rather than two unrelated carrier species. The left panel of the original sketch includes axes, $\Gamma$, and the three positive-axis X points; the negative-axis X points are symmetry-equivalent.
The surviving valence maximum lies roughly $1.2\,\mathrm{eV}$ below the original $\mu$. Lowering $\mu$ by $1.5\,\mathrm{eV}$ therefore places it in the upper <valence band> in the conventional <silicon> band interpretation. The electron pockets disappear and one sketches a <hole pocket> centred at $\Gamma$, as in the middle panel. Detailed valence-band warping and the number of spin-orbit-resolved sheets cannot be extracted from the damaged figure, and the single drawn surface is schematic rather than a claim that all such sheets coincide.
A discriminating physical property is the <Hall coefficient>: electron-dominated transport gives a negative value, whereas hole-dominated transport gives a positive value in the ordinary single-dominant-carrier regime. One should not infer a numerical resistivity change without the carrier densities and mobilities.
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