To farmers and gardeners, commercial fertilizers have a big three-number "npk" label on the bag that gives the amounts of three key plant nutrients: nitrogen, phosphorus and potassium. for example, a bag of fertilizer has by mass nitrogen, by mass potassium as potash , and by mass phosphorus as phosphate . suppose a certain fertilizer has the following composition: ingredient percent by mass calcium nitrate urea potassium sulfate inert ingredients

what should the first (nitrogen) number on the bag label be? that is, calculate the percent by mass of nitrogen in this fertilizer. round your answer to the nearest percent.