(b) Smart Kitchen sells and two different sets of dinner during this COVID-19 pandemic. The choice of dinner sets are Set A for 3-4 persons and Set B is for 5-6 persons in a family. Given x denotes number of Set A and y denotes number of Set B, the total revenue (, ) and the total cost (, ), both in Ringgit Malaysia are as follows:

(, ) = 120 + 110

(, ) = 16 2 16 + 8 2 24 + 78 + 200

Find the number of each set of dinner sets that must be sold in order to maximise its profit. What is the maximum profit realizable? (12 marks)