A vertical cylindrical tank has a diameter of 1m and a height of 2.50m. The tank, open at the top and is 3/5 full, is rotated about its vertical axis at a constant angular speed. At what angular velocity must the tank be rotated so that the diameter of the exposed surface at the bottom of the tank is 40cm?
choices: 145.94 , 149.00, 129.03, 135.19