You have been supplied with a concentrated solution of calcium dihydrogen phosphate to be used in a hydroponic system to grow lettuce. The solution has a phosphorus concentration of 200 mg/ L, however, in a hydroponic nutrient solution, the common range of elemental phosphorus required is 30-50 mg/L. Explain how you would prepare a solution containing 35 mg/L phosphorus in a 500 mL volume?