Is a banana turning brown when it is left on the counter a physical change?

Fertilizer is sold in 100 pound bags labelled with the amount of nitrogen ( n), phosphoric acid ( p2o5), and potash ( k2o) present. the mixture of these nutrients varies from one type of fertilizer to the next. for example, a 100100 pound bag of vigoro ultra turf fertilizer contains 2929 pounds of nitrogen, 33 pounds of phosphoric acid, and 44 pounds of potash. another type of fertilizer, parker's premium starter, has 1818 pounds of nitrogen, 2525 pounds of phosphoric acid, and 66 pounds of potash per 100100 pounds. determine the amount of each type required to yield a mixture containing the 112112 pounds of nitrogen, 8181 pounds of phosphoric acid, and 2626 pounds of potash.