Select the correct statement.

A polyatomic gas at pressure P , having volume ' $V$ ' expands isothermally to a volume ' 3 V ' and then adiabatically to a volume ' 24 V '. The final pressure of gas is (for moderate temperature changes)

A stationary object at $4^{\circ} \mathrm{C}$ and weighing 3.5 kg falls from a height of 2000 m on snow mountain at $0^{\circ} \mathrm{C}$. If the temperature of the object just before hitting the snow is $0^{\circ} \mathrm{C}$ and the object comes to rest immediately then the quantity of ice that melts is (Acceleration due to gravity $=10 \mathrm{~m} / \mathrm{s}^2$, Latent heat of ice $=3.5 \times 10^5 \mathrm{~J} / \mathrm{kg}$ )

Six molecules of a gas in container have speeds $2 \mathrm{~m} / \mathrm{s}, 5 \mathrm{~m} / \mathrm{s}, 3 \mathrm{~m} / \mathrm{s}, 6 \mathrm{~m} / \mathrm{s}, 3 \mathrm{~m} / \mathrm{s}$, and $5 \mathrm{~m} / \mathrm{s}$. The r.m.s. speed is