pls help

In order to prepare 100.mL of a 0.50M sodium phosphate buffer, pH7.0, how many grams of sodium phosphate monobasic must you add to your solution? For this buffer, both sodium phosphate monobasic and sodium phosphate dibasic are available. Use MW=137.99g/mol for sodium phosphate monobasic and pKa=7.2 for sodium phosphate In order to prepare 100.mL of a 0.50M sodium phosphate buffer, pH7.2, how many grams of sodium phosphate dibasic must you add to your solution? Both sodium phosphate monobasic and dibasic are available to make this buffer. Use MW=268.07g/mol for sodium phosphate dibasic and pKKa=7.2 for sodium phosphate