Antibiotic concentration from stock solution practice problem

An antibiotic (kanamycin) used during a conjugation experiment is stored as a stock solution of 10 mg/ml. You are pouring plates from a 500 ml flask of molten agar and need an antibiotic concentration of 20 μg/ml in the plates.

How many μl of the antibiotic stock need to be added to the agar to get the desired concentration?

μl need to be added