( b ) For an industry in Malaysian economy, the function of average cost (AC, RM thousand) is given as follows: AC = 0.1Q -8+ 500 where Q represents the number of outputs per year (thousand units). (i) Formulate the function of total cost (TC) in terms of Q. (4 marks) (ii) Prove and determine the amount of optimal output at which the minimum total cost occurs. (5 marks) (iii) Determine the minimum cost at optimal level from this industry. (2 marks) (iv) Sketch the function of TC. (6 marks)