Fluorine compounds are added to Melbourne's supplies of drinking water to give a concentration of fluoride ions of about 0.90ppm(1ppm=1g in 10^6g) （10的6次方）
a.what amount,in mol,of fluoride is present in 1.0g of Melbourne water?
b.How many fluoride ions would you swallow if you drank a 200ml glass of Melbourne water?(Recall 1ml of water weighs 1 g.)