A flask containing 12g of a gas of relative molecular mass 120 at a pressure of 100 atm , was evacuated by means of a pump untill the pressure was 0.01 atm at the same T. Which of the following is the best estimate of the number of molecules left in the flask. $(N_0 = 6\times10^{23} mol^{-1}$)

Question

$(a)\;6\times10^{19}\qquad(b)\;6\times10^{18}\qquad(c)\;6\times10^{17}\qquad(d)\;6\times10^{13}$