Lawnco produces three grades of commercial fertilizers. A 100 kg bag of grade-A fertilizer contains 18 kg of nitrogen, 4 kg of phosphate, and 5 kg of potassium. A 100 kg bag of grade-B fertilizer contains 20 kg of nitrogen and 4 kg each of phosphate and potassium. A 100 kg bag of grade-C fertilizer contains 24 kg of nitrogen, 3 kg of phosphate, and 6 kg of potassium. How many 100 kg bags of each of the three grades of fertilizers should Lawnco produce if 26400 kg of nitrogen, 4900 kg of phosphate, and 6200 kg of potassium are available and all the nutrients are used?