For this problem, we use the equation derived from Beer's Law as written below:
A = ∈LC,
where
A is the absorbance
∈ is the molar absorptivity
L is the path length of the cuvette
C is the concentration of the sample solution placed in the cuvette
To determine C, we have to know the rest of the parameters. Generally, the equation for C would be:
C = A/∈L = A/∈(1 cm)
C = A/∈
If you know the absorbance and the molar absorptivity in mol/L·cm, you can determine the value of C.