The following absorption data of a solution was collected in a cell with 1 cm path length. The absorption of the same substance in a solution with unknown concentration was 0.197. What is the concentration of the unknown substance?

c (M) A
1.00x10-3 0.119
2.00x10-3 0.243
3.00x10-3 0.376
4.00x10-3 0.484
5.00x10-3 0.630

I don't understand what c column means but if these are the concentrations and the A of five standards, I'm sure you are supposed to plot the data and use the graph to determine the concn of the unknown. Alternatively, you may consider calculating the constant, a, from A = abc for each of the five, determining the average value, and using the average value to determine c from A = abc. If the solution obeys Beer's Law and it is a straight line throughout, the calculation method will work ok; otherwise, it will not.