A: (40, 7)
B: (20, 7.4)
f = Line(B, A)
k(x) = (0.001 * x^(3)) - (0.1 * x^(2)) + (5 * x) + 80
u(x) = (-0.02 * x^(2)) + (7.8 * x)
a = IntegralBetween(u, k, 20, 100)
g(x) = u(x) - k(x)
C = Extremum(g, 40, 80)
D = Point(f)
h = Segment(C, D)