Why is Specific Gravity (SG) Needed in This Buoyancy Calculation?

[CyberneticsInside]

Homework Statement

[/B]
When asked for the bouancy of a hollow cylinder, containing air, submerged in ocean water.
outer radius R.
Length of cylinder = L
The Material of the cylinder is neglected.

I'm thinking the Bouancy (Force) = ρ ⋅ g ⋅ v
where v = LπR^2 and therefore F = ρgLπR^2

But the solutions manual states it is
F = ρgLπR^2 ⋅ SG, where SG is Specific gravity of ocean water.
Why do I need the SG part ?

 

[dubya_80]

The density of the water affects the buoyancy of the object.

 

[gneill]

Hi CybernetcInside,

In future, please use the entirely of the formatting template to lay out your questions.

Did the book define what the variable $\rho$ stands for in its solution? You didn't define it in your work.