${ }^{n} \mathrm{P}_{\mathbf{r}}=$ কত?

$\mathrm {\frac{\lfloor {n}}{ \lfloor {(n-r)}}}$

$\mathrm {\frac{\lfloor {n}}{ \lfloor {r} {~} \lfloor {(n-r)}}}$

$\mathrm {\frac{\lfloor {n}}{ \lfloor {r}}}$

$\mathrm {\frac{\lfloor {(n-r)}}{ \lfloor {r}}}$