Ure = 90
Skupni cas = p + d
U = 3*sqrt(d) + 6*sqrt(p)

u = ?
d = ?

p = 90-d
U = 3*sqrt(d) + 6*sqrt(90-d)

U' = \frac{3}{2\sqrt{d}}-\frac{3}{\sqrt{90-d}}

0 = \frac{3}{2\sqrt{d}}-\frac{3}{\sqrt{90-d}}

d = 18

90 = p + 18

p = 90 - 18 = 72