A 2 litre glass flask contains some mercury. It is found that at all temperatures, the volume of air inside the flask, remains the same. The volume of mercury inside the flask is  α   for  glass = 9 × 10−6/0C, and for mercury =  1.8  ×  10−4/0C)

Since volume of air in the flask remains the same, the expansion in volume of vessel is exactly equal to the volume Expansion of mercury∴    ΔVV   =  ΔVm⇒    VV .  γv .  ΔT  =  Vm  .  γm .  ΔT⇒    Vm  =  Vv .  γvγm  =  Vm  × 3αγm⇒    Vm  =  2000 ×  3 × 9 ×10−61.8 × 10−4  cc= 300cc