The invention of a self milking cow machine allows cows to milk themselves. Not only does this reduce the need for higher cost human assistance in milking, but it also allows the cow to milk herself three times a day instead of two, leading to both a healthier cow and increased milk production

a. show the effect of this innovation on the equilibrium quantity and price of milk

b. show the likely effect on equilibrium price and quantity of apple juice (a substitute for milk)