By weight, one fertilizer is 10% potassium, 40% nitrogen, and 50% phosphorus. a second fertilizer has percent of 10, 20, and 70, respectively, and a third fertilizer has
percents of 0, 30, and 70, respectively. how much of each must be mixed to get 200 lb of fertilizer with percents of 8.5, 27.5, and 64, respectively?
one must mix b of the first mixture,

b of the second mixture, and
i of the third mixture to obtain the desired result