Suppose there are four people with hats entering a meeting, and they entrust their hats to a hat-check person. After the meeting, the hat-check person gets completely confused and randomly hands back hats to these same four people so that everyone gets a hat. In particular, each possible way to hand back the hats is equally likely. Let the random variable X be the number of hats returned to their rightful owners. (For example, if the hats of people a,b,c,d are respectively given to a,c,b,d then X would have the value 2.) Compute the expected value of X , the variance of X and the standard deviation of X .