Determining the percentage of acetylsalicylic acid in an aspirin tablet...?

If I have an aspirin tablet that weighs 0.4g and I boil the aspirin with 2mL of 1M sodium hydroxide solution and 10mL of water. I then dilute the solution to 100mL. How would I find the concentration of this solution when all I have is the m of the aspirin tablet? I am then asked to transfer 1mL of this solution to a 50mL volumetric flask and add a 0.02M FeCl3 solution until the graduation mark of the flask (total 50mL). If I don't have the concentration of the orignal solution, how would I find it for this?HELP PLEASE!!