In order to determine equilibrium mathematically, remember that quantity demanded must equal quantity supplied. The demand for dog treats is represented by the following equation: QD=300-50P. In the equation, QD represents the quantity demanded of dog treats, and P represents the price of a box of dog treats in dollars. Because a negative sign is in front of the term 50P, as price increases, quantity demanded decreases. The supply of dog treats is represented by QS=-100+150P. The quantity supplied of dog treats is represented by QS in this equation, and P again represents the price for a box of dog treats in dollars. A positive sign in front of the 150P indicates a direct relationship exist between price and quantity supplied. Using the word problem, calculate the equilibrium price for dog treats. Which of the following answers would be the correct equilibrium price?