A float value of the ‘ball – cock’ is required to close an opening of a supply pipe feeding a cistern as shown in the given figure.
The buoyant force FB required to be exerted by the float to keep the valve closed against a pressure of
0.28 N/mm2 is
(a) 4.4 N (b) 5.6 N (c) 7.5 N (d) 9.2 N