Ok, looking at part A first::
Total anticipated sales revenue will be £18.00 x 20,000 units = £360,000
Target total operating profit will be £360,000 x 25% = 90,000
Target total costs will be £360,000 - £90,000 = £270,000
Target cost per unit (to 2 decimal places) will be £270,000 / 20,000 units = £13.50
For part B you follow the same principles:
Target operating profit will be 17.00 x 25% = £4.25
Target total cost per unit will be £17.00 - £4.25 - £12.75
Target fixed costs will be £12.75 - £7.00 = £5.75
(in case you need to enter the figure for manufacturing costs in any other practice papers, use the £140,000 (provided in the table at the top under variable manufacturing costs) and divide it by the number of units - so £140,000 / 20,000 units = £7)
For the last part, use the figures given in the table at the top.
You need to know the total costs for the production of 20,000 so 65,000 + 140,000 + 45,000 + 35,000 = £285,000
Less the variable costs (also in the table) will be £285,000 - £140,000 = £145,000 fixed costs
You need to divide the fixed costs by the number of units so £145,000 / 20,000 = £7.25 per unit
You can now complete the calculation by taking £145,000 / 5.75 (from first part of answer
= 25217.39 rounded to 25217 as you need to show full units not parts of units.
Hope that helps.