the kenya agricultural research insistute suggested to a farmer to spread out at least 4800kg of a special phosphate and not less than 7200kg of a nitrogen fertilizer to raise productivity of crops in his fields. there are two sources to obtain these mixtures A and B. both of these are available in bags weighing 100 kg each and they cost 116, 400 respectively, while mixture B contains these ingredients equivalent to 50kg each. determine how many bags of each type the farmer should buy in order to obtain the required fertilizer at minimum cost.