Two cars are travelling towards each other at speed of \( 20 \, \text{m s}^{-1} \) each. When the cars are \( 300 \, \text{m} \) apart, both the drivers apply brakes and the cars retard at the rate of \( 2 \, \text{m s}^{-2} \). The distance between them when they come to rest is:
