Could somebody help me & explain to me the step by step procedure of this problem?

Answer A=.01925kg B= 0.7123 kg C= 1.886 kPa


A 6 m^3 tank contains helium at 400K and is evacuated from atmospheric pressure to a pressure of 740 mm Hg vacuum. Determine (A) mass of helium remaining in the tank, (cool.gif mass of helium pump out, © the temperature of the helium falls to 10 degrees Centigrade. What is the pressure in kPa?

your help is highly appreciated.