Notice that this problem involves three variables: mass, density and volume. These three are related through this formula:
Density = Mass/Volume
So, to find for mass,
Mass = Density*Volume
The volume can be calculated using the dimensions.
V = 0.1865 cm x 5.75 cm x 8.8 cm = 9.44 cm³
Now, the density is a constant value for solids. Since card stock is made of paper, we can use the density of paper: 0.25 g/cm³. Thus,
Mass = 0.25 g/cm³ * 9.44 cm³
Mass = 2.36 g
