Key TakeawaysCarMax missed quarterly profit and sales estimates amid slowing demand caused by what it called "vehicle affordability challenges."The used-car retailer sold more retail vehicles, but at lower prices. Wholesale vehicle sales dropped, along with prices.CarMax pushed back its goal to sell at least 2 million vehicles annually. CarMax (KMX) shares plunged Thursday after the biggest U.S. used-car retailer posted weaker-than-expected quarterly results amid slowing demand. The company reported fourth- ...