Todd uses the quadratic regression model to determine the predictive average unit cost of baseballs produced in his production facility. After determining predictive average costs at multiple unit batch size amounts in millions, he now wants to know what the output level that maximizes his costs would be. Given b1=0.3904 and b2=0.0247, what is the level that will maximize his average cost in units? Multiple Choice 7.90 million units 7.2 million units 2.8 million units 20.40 million units