The rotational constant and the fundamental vibrational frequency of $\mathrm{HBr}$ are, respectively, $10\,\mathrm{cm^{-1}}$ and $2000\,\mathrm{cm^{-1}}$. The corresponding values for $\mathrm{DBr}$ approximately are
(a)$20\,\mathrm{cm^{-1}}$ and $2000\,\mathrm{cm^{-1}}$
(b)$10\,\mathrm{cm^{-1}}$ and $1410\,\mathrm{cm^{-1}}$
(c)$5\,\mathrm{cm^{-1}}$ and $2000\,\mathrm{cm^{-1}}$
(d)$5\,\mathrm{cm^{-1}}$ and $1410\,\mathrm{cm^{-1}}$