I have attached 2 screenshots, these are related with each other. One of them is giving info, another one contains questions. Could you please explain a and b with clear step by step solution? Please, do not write only answer.Could you please provide step by step solution for iii) and iv) ?

(iii) (10 marks) Now assume that U(:r,y) = my, Pan = 1, PM = 4 and B = 120. Find A\" along with the optimal levels of 1" and y'. Calculate U\". (iv) (9 marks) Using the Bordered Hessian matrix, verify that the secondorder conditions for a maximum are satised. (0.) Consider the following optimization problem: max U = U (3:, 3;) subject to mm + my = B where pmpy and B are constants. (For your reference, the above model is very common in both Micro and Macro. This is called a standard utility maximization problem. U is the consumer's payoff or utility which is a function of the quantities of two goods 3: and y, B represents the consumers's available income (or, budget constraint) and, Pa and P1, denote the prices of good a: and g, respectively.)