Denise should receive £7, and Malcolm £1. Suppose the
cups they used each have a capacity of a third of a litre. Then because
there were eight litres in total, each of the three drank eight cupfuls of
water that day. Denise had a total of fifteen cupfuls, having eight to
herself and giving seven to Joel. Malcolm, on the other hand, gave only
one cup to Joel out of the nine that he could make out of his supply.