An advertising blimp consists of a gas bag, the supporting structure for the gas bag, and the gondola hung from the bottom, with its cabin, engines, and propellers. The gas bag is about 30 meters long with a diameter of about 10 meters, and it is filled with helium (density about 4 grams per 22.4 liters under these conditions). Estimate the total mass of the blimp, including the helium.