What is the density of aluminum chloride vapor (AlCl3) at 498 K and 0.939 atm?

(06.06 MC)

What is the density of aluminum chloride vapor (AlCl3) at 498 K and 0.939 atm?

a.  1.24 g/L
b.  3.06 g/L
c.  5.17 g/L
d.  7.42 g/L