Online lottery to decide the order of appearance

(i) (ii) The mathematical expectation of a random variable is.

Test analysis: (1) Assuming that "Team A and Team B are just in the top two" is an event, then

So the probability that Team A and Team B are just in the top two is.

(ii) The possible values of a random variable are.

,

,

,

. ?

The distribution list of random variables is:

Because,

So the mathematical expectation of random variables is.

Comments: The key to calculating the probability of possible events such as this question is to list the basic event space correctly according to the meaning of the question and get the number of basic events it contains.