What is the surface tension of gasoline if the height of its rise in a tube with a radius of 0.2 mm is 3 cm?

R = 0.2 mm = 2 * 10 ^ -4 m.
h = 3 cm = 3 * 10 ^ -2 m.
ρ = 700 kg / m ^ 3.
g = 9.8 m / s ^ 2.
σ -?
The height of the liquid rise in the capillary is determined by the formula: h = 2 * σ / R * ρ * g.
Where σ is the surface tension, R is the radius of the capillary, ρ is the density of the liquid in the capillary, g is the acceleration of gravity.
σ = R * ρ * g * h / 2.
σ = 2 * 10 ^ -4 m * 700 kg / m ^ 3 * 9.8 m / s ^ 2 * 3 * 10 ^ -2 m / 2 = 0.02 N / m.
Answer: the surface tension of gasoline in the tube is σ = 0.02 N / m.