Budgeted production for the month was 5,000 units although the company managed to produce 5,800 units, selling 5,200 of them and incurring fixed overhead costs of £27,400 while selling price £75. What is the operating margin using marginal costing if contribution margin ratio is 40%?
a. £128,600 

b. £183,400
c. £146,600 

d. None of the above