Which hybrid orbitals are used by nitrogen atoms in the following species? a$)$ N$*$H$\_\{3\}$ sp s $*$ p $^2$; s $*$ p $^3($b$)$ H$\_\{2\}*$N $-$ N$*$H$\_\{2\}$ sp s $*$ p $^2$; s $*$ p $^3($c$)$ NO $3^-$; s $*$ p $^2$ sp s $*$ p $^3$