How Much Air Is Needed to Lift a Sunken Steel Ship?

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To lift a sunken steel ship weighing 500,000 kg, air bags must be inflated inside the hull to displace enough water. The specific gravity of steel is 7.8, leading to a density of 7800 kg/m^3. The volume of the ship can be calculated using its mass and the density of steel, which is approximately 64.1 m^3. The volume of air required to lift the ship must equal the volume of water displaced, which is equal to the weight of the ship. The calculations indicate that the correct volume of air needed is 872 m^3.
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A sunken steel ship has a mass of 500,000 kg. It is filled with water. In order to lift the ship, air bags are to be inflated inside the hull. What volume of air is needed if 7.8 is the specific gravity of steel?

A- 436 m^3
B- 2778 m^3
C- 1266 m^3
D- 872 m^3
E- 225 m^3

so since the specific gravity is 7.8, the density of steel is 7800 kg/m^3. but i don't know what to do next. how do you find the volume of air? i tried making the force of air pushing up equal to the force of the ship pulling down so that (density of air)(volume of air) = (density of steel)(volume of steel) but i get the volume is none of the choices above. please help.
 
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Mass of the ship and density of steel is given.
Find the volume of the ship.
This volume and the volume of the balloon will be the volume of the displaced water.
Weight of the displaced water must be equal to the weight of the ship.
 
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