A car of mass $1000 \mathrm{~kg}$ has a motor of efficiency $20 \%$. If burning of one litre of petrol supplies $6 \times 10^7 \mathrm{~J}$ of energy, the amount of petrol used in accelerating the car from rest to $43.2 \mathrm{~km} \mathrm{~h}^{-1}$ is