A spherical balloon of 21cm diameter is to be filled up with $H_2$ at NTP from a cylinder containing the gas at 20 atm at $27^{\large\circ}C$. The cylinder can hold 2.82 litre of water at NTP . Calculate the number of balloons that can be filled up.

Question

$(a)\;11\qquad(b)\;10\qquad(c)\;9\qquad(d)\;4$