B(x) = If[2 ≤ x ≤ 12, (-x^(3)) + (15 * x^(2)) - (38.25 * x)]
B'(x) = If[2 ≤ x ≤ 12, ((-3 * (x - 1.5)) * (x - 8.5))]
a: B(2)
b: B(8.5)
c: B(12)
A = Intersect(B', xAxis)