It turns out that the van der Waals constant b equals four times the total volume actually

Question:

It turns out that the van der Waals constant b equals four times the total volume actually occupied by the molecules of a mole of gas. Using this figure, calculate the fraction of the volume in a container actually occupied by Ar atoms
(a) At STP,
(b) At 200 atm pressure and 0oC. (Assume for simplicity that the ideal-gas equation still holds.)