5. It is estimated that if a price of $15 per unit is charged for a product, five units per period will be sold. If the price is lowered to $13, sales will be six units per period. The supply curve for the product is given by P=3+5. a) Assuming that the demand relationship is linear, find the demand equation. b) Find the equilibrium price and quantity (i.e. the price where quantity demanded = quantity supplied)