a transport company has two types of trucks; mack $375 and chevrolet R28s. Macks have a refrigerated capacity of 15 m 3 and a non-refrigerated capacity of 45m while R28s have the same overall volume with equal sections for refrigerated and non-refrigerated stock. a grocer needs to hire trucks for the transport of 4,000m3 of refrigerated stock and 3,000 m3 of non-refrigerated stock. the cost of renting a mack is $350, while the cost of renting a chevrolet is $400. how many trucks of each type should the grocer rent to achieve the minimum total cost?