What is the density of the glass making up the beaker?

The answer is 2786 kg/m^3

How do you do this? argh i got my final tomorrow =S

**1. The problem statement, all variables and given/known data**

mass of beaker=0.39 kg

density of water is 1000 kg/m^3

interior volume of beaker is 500 cm^2

**2. Relevant equations**

Fb= density*g* Volume displaced

**3. The attempt at a solution**

i don't know how to do this AT ALL!