Moon Karak sells tea. The average selling price of a cup is OMR 0.200 and the average variable expense per cup is OMR 0.150. The average fixed expense per month is OMR 800. An average of 20,000 cups are sold each month. What is the margin of safety expressed as a percentage of sales? Select one: O a. None of the answers given Ob. 20% O c. 15% O d. 10% O e. 5%