A lorry which is going to travel abroad is being loaded in London. At the loading
depot it will visit each of N bays once; at each of these a number of items of a single
type will be loaded. The volume of the lorry is W, and the volume of an item of
type i is wi. On delivery an item of type i can be sold for bi. The company wishes
to maximise the value of the load.
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Everywhere is walking distance if you have the time.