John drives from London to Liverpool via Birmingham. The distance between London and Birmingham is 125 kilometres. The distance between Birmingham and Liverpool is 100 kilometres. John drives at an average speed of 50 km/h between London and Birmingham. He plans to take 30 minutes rest in Birmingham before driving to Liverpool. It then takes him a further 4 hours to to reach Liverpool due to bad traffic. What is John's average speed for the whole journey? Give your answer to 3 significant figures. ​