A doctor records for 400 hospital patients selected at random, note the pair of information: (temperature when admitted, temperature 24 hours later). He finds that the average patients' temperature upon admission is 101 degrees and 99 degrees 24 hours later. The standard deviation is 1.5 degrees for temperatures when admitted and 0.5 degrees for those the next day. The correlation between the two temperatures is 0.8. What so the covariance between the variables?