A glass tube contains an equal number of moles of helium and argon. After five minutes, half of the particles escape through a small hole in the glass. What are the relative amounts of helium and argon in the tube at five minutes?

(a) The tube still contains an equal number of moles of helium and argon.

(b) The tube contains a greater number of moles of helium than argon.

(c) The tube contains a greater number of moles of argon than helium.