When Carla made $400 each month, she bought 40 units of food at $10 per unit and no shelter, which cost $20 a unit. Then she received a raise to $600 each month and she began consuming 30 units of food at the same price and 15 units of shelter, which still cost $20 per unit. Sketch Carla's income- consumption curve for food. Also sketch her Engel curve for food and indicate whether food is a normal or inferior good.