As from the formula, $v_{ rms }=\sqrt{\frac{3 R T}{M}}$
Given that $\left(v_{ rms }\right)_{\infty}=1000\, m / s$
$( Temp .)_{ CO }=27^{\circ} C =300 K$
(Temp.) $_{ N _{2}}=600\, K$
Now putting the values, we get
$\frac{\left(v_{ rms }\right)_{ CO }}{\left(v_{ rms }\right)_{ N _{2}}}=\sqrt{\frac{3 R}{3 R} \times \frac{T_{ CO }}{M_{ CO }} \times \frac{M_{ N _{2}}}{T_{ N _{2}}}}$
$\frac{1000}{\left(v_{m s}\right)_{N_{2}}}=\sqrt{\frac{300}{28} \times \frac{28}{600}}$
$=\frac{1}{\sqrt{2}}$
or, $\left(v_{ ms }\right)_{ N _{2}}=1000 \times 1.414$
$=1414\, m / s$