b. A yoghurt pot can be approximated to a cylinder that is open at one end, with the following dimensions: height 78 mm, external diameter 90 mm and constant material thickness 0.3 mm. This is illustrated below. 0.3 mm 90 mm 78 mm 0.3 mm Figure 3 Cylinder used to represent the yoghurt pot (not drawn to scale) Hide description The drawn diagram shows a cylinder. The top end of the cylinder is open. The dimensions of the cylinder are labelled as follows: the thickness of the cylinder wall is labelled as 0.3 mm; the height of the cylinder is labelled as 78 mm; the external diameter of the cylinder is labelled as 90 mm. i. Given that the density of PP is 900 kg m-, calculate the mass of one of the yoghurt pots in grams to 1 decimal place. ii. A different manufacturer makes yoghurt pots which weigh 9 grams each. Assuming each empty pot has a sale value of 3 pence, estimate the value added from the transformation of one tonne of PP granules into yoghurt pots. You can assume that a tonne of PP granules costs 1900 and there is no waste in the manufacturing process. Explain each step in your working. (10 marks) c. As an alternative, yoghurt is occasionally sold in glass jars. Compare the two materials and give two advantages and two disadvantages for using glass rather than PP. (10 marks) d. The chemical formula for one repeat unit of the PP polymer is C3H6. Write down a balanced chemical equation for the complete combustion of one repeat unit of PP in oxygen to form carbon dioxide and water (you may find it helpful to show the steps in your working as described in Section 6.2, Part 2 'Engineering for power'). Explain how you can test that your equation is balanced. (6 marks) e. The heat of combustion of PP is 38.7 MJ kg-1. If PP containers are burned in a waste- fired power station that generates electricity with an overall efficiency of 19%, calculate how much useful electrical energy is generated when 1,000 tonnes of PP is burned. Give your answer in units of MJ to 3 significant figures and explain your working. (5 marks)