\(\mathrm{v}^{\prime}=\mathrm{v}\left(\frac{v+v_{o}}{v-v_{s}}\right)\)
where \(v=\) velocity of sound
\(v_{o}=\) velocity of observer, \(i . e .,\) second car
\(v_{s}=\) velocity of source \(i . e .,\) first car
\(v^{\prime}=400\left(\frac{340+16.5}{340-22}\right)=400\left(\frac{356.5}{318}\right)\)
\(v^{\prime} \approx 448 \mathrm{Hz}\)