Two narrow bores of diameters 3.0 mm and 6.0 mm are joined together to form a U-shaped tube open at both ends. If the U-tube contains water, what is the difference in its levels in the two limbs of the tube? Surface tension of water at the temperature of the experiment is 7.3×10⁻² Nm⁻¹ Take the angle of contact to be zero and density of water to be 1.0×10³kgm³ (g=9.8ms−2)

a. 3 mm
b. 2 mm
c. 4 mm
d. 5.0 mm