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10. (9 marks) (For this question you must show your work!) Maria owns a coffee shop. On average, for every sale of large coffee she sells 4 small coffees. Sales price of small coffee is $2.80 and for large coffee is $4.00. The average variable expense of making one small coffee is $0.70 and for one large coffee is $0.80. Maria's coffee shop has a fixed monthly expense of $4,640. a. How many coffees should she sell in a month to Break-Even? b. How many coffees should Maria sell to have an operating income of $2,320 for the month? c. If suppliers increase the price of coffee beans so that the variable cost of making each coffee size increases by 10%, how many additional units should Maria sell to achieve the above operating income