There is water in a round reservoir with an open top. The water pressure is measured with a mercury manometer connected to the reservoir as shown in the figure below. On the left arm of the manometer, the mercury level is 
lower than the centre of the sphere. The right arm of the manometer is open at the top and the mercury level is 
higher than on the left arm. What is the radius of the reservoir?
The density of mercury is 
and the density of water is 
.
Round reservoir with water and mercury manometer
.
