Subtract the volume of the inside diameter from the volume of the outside diameter and then multiply that by the density.
Volume of outside:
PI x 1.8^2 x 3.9 = 39.67704 cubic cm
Volume of inside:
PI x 1.35^2 x 3.9 = 22.318335 cubic cm
Difference: 39.67704 - 22.318335 = 17.358705 cubic cm.
Mass = 17.358705 x 8 = 138.86964 grams. Round the answer as needed.
