The mean
free path of CO under these new conditions is 52000 m ( = 5.2
x 10^{4} m)

**Rationale**

The mean free path of molecules in the gas phase is inversely
proportional to the pressure , hence when the pressure of the
gas is reduced by 5 decades from 10^{-4} Torr to 10^{-9}
Torr, the mean free path will increase by a factor of 100000.

i.e. λ = 0.52 x 100000 = 5.2
x 10^{4} m