can anyone solve this on paper for me

23. A 1:10 dilution of plasma was used to make serial dilutions. One mL of the first dilution was added to 4mLs of water. The second dilution was mixed, and one mL of this solution was added to 4mL of water (third dilution). The third dilution was mixed, and one mL of this solution was added to 4mL of water (fourth dilution). What is the dilution of plasma in the fourth tube