I don't understand how they got that answer

Table 10-2 Quantity of Total Utility MU MU/P Quantity of MU MU/P Soup (cups) (Soup) Total Utility (Sand) 1 Sandwiches 40 1 45 60 10 N 137 20 75 30 10 72 12 3 102 27 9 4 82 10 5 4 120 18 6 5 88 6 3 135 15 5> 6 90 2 6 145 10 3.33 Table 10-2 above shows Keira's utility from soup and sandwiches. The price of soup is $2 per cup and the price of a sandwich is $3. Keira has $18 to spend on these two goods. 19) Refer to Table 10-2. If Keira maximizes her utility, how many units of each good should she buy? A) 1 cup of soup and 5 sandwiches B) 3 cups of soup and 4 sandwiches C) 6 cups of soup and 2 sandwiches D) 4 cups of soup and 3.5 sandwiches Answer: B IC Explanation: Coylengq mi nwode tocham Cost of 2 Soup and 2 Sandwich = 2*2 + 2*3 = 10 () lousy ni nworks roshan ality Cost of 3 Soup and 4 Sandwich = 3*2 + 4*3 =(18 Voo was evads and to fLAB Cost of 4 Soup and 5 Sandwich = 4*2 + 5*3 = 8+15 = 23v X So, would choose B. d 8