17 The table shows the height, in metres, above sea level of the highest and lowest points in some continents. A negative value indicates a point below sea level. (a) What is the height above sea level of the highest point in Africa? Give your answer in kilometres. (b) In South America, how much higher is the highest point than the lowest point? Give your answer in metres. (c) How much higher is the lowest point in Europe than the lowest point in Asia? Give your answer in metres.