A vacuum chamber designed to be pumped down to a pressure of 10^-4 Pa has stainless steel walls that are 3 mm thick. You must design a new chamber that can be pumped down to a pressure of 10^-5 Pa. How thick must the walls of the new chamber be?

1. 0.3 mm
2. 3 mm
3. 1 cm
4. 3 cm