What is the total number of tetrahedral voids in $0.6 \ mole$ of a compound that forms a $hcp$ structure?

The number of tetrahedral and octahedral voids in a $CCP$ unit cell are respectively:

In hexagonal systems of crystals,a frequently encountered arrangement of atoms is described as a hexagonal prism. Here,the top and bottom of the cell are regular hexagons and three atoms are sandwiched in between them. $A$ space-filling model of this structure,called hexagonal close-packed $(HCP)$,is constituted of a sphere on a flat surface surrounded in the same plane by six identical spheres as closely as possible. Three spheres are then placed over the first layer so that they touch each other and represent the second layer. Each one of these three spheres touches three spheres of the bottom layer. Finally,the second layer is covered with a third layer that is identical to the bottom layer in relative position. Assume radius of every sphere to be $r$.
$1.$ The number of atoms on this $HCP$ unit cell is
$(A)$ $4$ $(B)$ $6$ $(C)$ $12$ $(D)$ $17$
$2.$ The volume of this $HCP$ unit cell is
$(A)$ $24 \sqrt{2} r^3$ $(B)$ $16 \sqrt{2} r^3$
$(C)$ $12 \sqrt{2} r^3$ $(D)$ $\frac{64 r^3}{3 \sqrt{3}}$
$3.$ The empty space in this $HCP$ unit cell is
$(A)$ $74 \%$ $(B)$ $47.6 \%$ $(C)$ $32 \%$ $(D)$ $26 \%$
Give the answer for questions $1, 2$ and $3.$

Which of the following represents the hexagonal close-packed $(HCP)$ arrangement of spheres?

Which of the following statements is not correct?

In chrysoberyl,a compound containing beryllium,aluminium and oxygen,oxide ions form a cubic close-packed structure. Aluminium ions occupy $\frac{1}{4}$ of the octahedral voids and beryllium ions occupy $\frac{1}{8}$ of the tetrahedral voids. The formula of the compound is