Wentworth Ltd sold 100 000 1 litre bottles of mineral water last year at $4 per unit and made a profit of $50 000. This year the costs for Wentworth Ltd remained the same, it sold 120 000 units at the same price, and made a profit of $80 000. Required Determine the total fixed costs per year and the total variable cost per unit for Wentworth Ltd using the high-low method. Write an equation for the cost function based on your answer to (a).