A fruit grower can use two types of fertilizer in his garden, brand P and brand Q The amounts (in kg) of nitrogen, phosphoric acid, potash, and chlorine in a bag of
each brand are given in the table Tests indicate that the garden needs at least
240 kg of phosphoric acid, at least 270 kg of potash and at most 310 kg of
chlorine If the grower wants to minimise the amount of nitrogen added to the garden,
how many bags of each brand should be used