please can I get some help with this question? A, B and C

3 a) Discuss why the pre-polymer reaction approach is to be preferred to the one- pot reaction approach for the synthesis of polyurethanes. b) You are working for a company producing air filters made of polyurethane fibres. A client wants a filter based on nanofibres. i) Which method would you use to prepare polyurethane nanofibres and why? ii) How would you optimise the process identified at point (i) to make it suitable for fibre production at industrial scale? c) a A rectangular slabstock polyurethane foam (1.2 x 0.8 m2) with a thickness of 0.3 m is characterised by a porosity of 65%. Determine the volume of the porous fraction (Vp) and the volume of the solid fraction (Vs). Considering that the mass (M) of the foam is 12 kg, determine its density (pbulk)