Utilize the Henderson - Hasselbalch equation to calculate the molar ratio of HP0_4^2, /H_2P0_4 (pKa 6.86) required to produce a phosphate buffer. From this molar ratio, calculate the grams of both sodium phosphate dibasic heptahydrate (Na_2HPO_4.7H_2O; FW 268.07) and sodium phosphate monobasic (NaH_2P0_4; FW 119.98) required to make 650 mL of 70 mM phosphate buffer, pH 7.3.