The formula to calculate the mass in milligrams (M) is:
\[ \text{M} = \text{V} \times \text{D} \]
Where:
Let's say the volume (V) is 10 cm3 and the density (D) is 2 mg/cm3. Using the formula:
\[ \text{M} = 10 \times 2 = 20 \, \text{mg} \]
So, the mass is 20 mg.