2 A tunnelling machine drills 500 metres. Use your values from the table to estimate the cost of drilling if the firstmetre costs
£X and each extra metre costs £Y.

Water at the rate of 1 kg/s is forced through a tube with a 2.5 cm inner diameter. the inlet water temperature is 15°c, and the outlet water temperature is 50°c. the tube wall temperature is 14°c higher than the local water temperature all along the length of the tube. what is the length of the tube?