Describe the shapes of $BF_3$ and $BH_4^-$. Assign the hybridisation of boron in these species.

(N/A) $(i)$ $BF_3$: Boron in $BF_3$ is $sp^2$ hybridised. It has a planar triangular geometry. The three $sp^2$ hybrid orbitals of boron overlap with the $p$-orbitals of three fluorine atoms.
$(ii)$ $BH_4^-$: Boron in $BH_4^-$ is $sp^3$ hybridised. It has a tetrahedral geometry,where the four $sp^3$ hybrid orbitals of boron overlap with the $1s$ orbitals of four hydrogen atoms.