part 2 needs to be a differential mass balance

A chamber with volume 15m3 has a leak into the atmosphere at sea level. The ideal gas, with a molar mass of 21g/mol, initially at 5atm and 325K, leaks out at a rate proportional to PP0 (where P0 is the pressure of the surroundings) with proportionality constant k=3.53gatm1s1 and P is pressure. Assume the process is isothermal. 1) Is this process at steady state, why or why not? 2) What is the mass of gas inside the chamber after 30 seconds? 3) How long until this process gets to 1.01atm ? 4) Bonus: When does P equal P0