Question: BRAIN GROWTH AND IQS In a study conducted at the National Institute of Mental Health, researchers followed the development of the cortex, the thinking part of the brain, in 307 children. Using repeated magnetic resonance imaging scans from childhood to the latter teens, they measured the thickness (in millimeters) of the cortex of children of age t yr with the highest IQs-121 to 149. These data lead to the model
S(t) = 0.000989t3 - 0.0486t2 + 0.7116t + 1.46 (5 ≤ t ≤ 19)
Show that the cortex of children with superior intelligence reaches maximum thickness around age 11.