5.6 litre of an unknown gas at NTP requires 12.5 calorie to raise its temperature by $10^{\large\circ}C$ at constant volume. Calculate the $C_v$ of the gas.

Question

$(a)\;3\;calorie\qquad(b)\;5\;calorie\qquad(c)\;7\;calorie\qquad(d)\;9\;calorie$