When a cylindrical capillary glass tube, open at both ends, is vertically inserted in a pool of water, the water level in the tube rises to 7 cm relative to the water level outside the tube. Consider that the surface tension of water is 0.07 N m⁻¹ and that the contact angle of water on glass is 0°. The density of water is 1000 kg m⁻³, and the local acceleration due to gravity is 10 m s⁻². The diameter of the capillary tube (in µm) is __________ (rounded off to the nearest integer).