Two capillary tubes with radii of 0.1 mm and 0.04 mm are immersed in a liquid with a density of 791.4 kg/m^3. After the liquid rises in the capillary tubes, the height difference between the liquid columns is measured, which is 8.9 cm. Default: contact angle 0. a) Calculate the surface tension of the liquid. b) In which capillary tube does the liquid rise higher?