The following example illustrates the consumption possibilities of a consumer under various income levels at fixed prices of Good X and Y. Good X (price=1) total quantity utility 1 23456 3 7 Required; 8 15 21 26 30 33 35 marginal utility Good Y (price =2) total quantity utility 1 2 34567 3 5 6 10 18 24 28 31 33 34 marginal utility a) Calculate the marginal utilities of X and Y (7 marks) b) Calculate the total sum of income at the utility maximization level (8 marks)