0.1575 g of anhydrous potassium dihydrogenphosphate are used to prepare 500 mL of the 50 mg/L (approximate) stock solution of P. The instructions guide you to make a subsequent STANDARD P solution. Following the procedure described in the lab manual, what is the volume you must use of STANDARD P solution to make a 100 μg/L P standard?

The answer is 1.395, but I don’t the way to get that answer.