Neutrophils are the most common type of white blood cell, comprising about 50-70% of all white blood cells. They are phagocytic, meaning that they can ingest other cells, though they do not survive the act. Neutrophils are the first immune cells to arrive at a site of infection, through a process known as chemotaxis.
One of the basic theories stipulates that increasing interest rates raise consumers' and manufacturers' costs, which, in turn, reduces the amount of time and money people spend driving. Less people on the road translates to less demand for oil, which can cause oil prices to drop.
Disasters like Hurricane in the Gulf of Mexico and surrounding cities in USA along the gulf may also increase the price of oil. Once the price of crude increases, it is time to sell it off. If the price of a barrel of crude was at $78 and it increased to $100 or more, I believe you know how much you would have gained.