Isokostenfunktion
20·x + 15·y = k
y = Ik(x) = (k - 20·x)/15
Acker1: 20·6 + 15·6 = 210
Acker2: 20·5 + 15·7 = 205
Acker3: 20·8 + 15·5 = 235
k = 20·x + 15·(12/(x - 2) + 3) = 180/(x - 2) + 20·x + 45
k' = 20 - 180/(x - 2)^2 = 0 --> x = 5 (∨ x = -1)
y = 12/(5 - 2) + 3 = 7
k = 180/(5 - 2) + 20·5 + 45 = 205