The market for a product has the following demand and supply equations: Qd=500−50P and Qs=150+25P, where Qd and Qs represent the quantity demanded and supplied respectively, and P represents the price of the product in dollars. If the market price is set at $4, what is the excess demand (shortage) in this market? Group of answer choices 50 units 100 units 150 units 200 units