Part (b) asked for a calculation of the optimum selling price for the new product and the resulting profit, using the formula: P = a-bx. There were some good answers here.

On the whole, the main reason for losing marks was because candidates confused sales volume maximisation with profit maximisation, thus using MR=0 to work out their answer rather than MC=MR.

Another reason for losing marks was forgetting to work out the resulting profit, just stopping at an optimum price and quantity. This was unfortunate as this was where the easy marks were in part (b).

Candidates are advised to always reread a requirement when they think they have finished answering it and briefly reflect on whether they have answered every part of it.