A factory has the following information: Sales units 6500 units 11500 units Total costs $215 600 $321 200 Sales revenue $325 000 $575 000 a.) Calculate the margin of safety in dollars if current sales is 10 000 units and explain your answer. (6 marks) b.) Calculate the operating income before tax if output units are 9540 units assuming selling price and variable cost per unit remained the same. (2 marks)