A 0.400g sample of toothpaste was boiled with a 50mL solution containing a citrate buffer and NaCl to extract the fluoride ion. After cooling, the solution was diluted to 100.0mL. The potential of a fluoride selective electrode SCE system in a 25.00mL aliquot of the sample was found to be -0.1446V. Addition of 5.00mL of a solution containing 0.00107 mg_F/mL caused the potential to change to -0.1823V. Calculate the % F (w/w) in the sample.