Two players A and B practice shooting training independently. According to past results, their shooting results are distributed as follows: Player A Player B Ring number 8 9 10 Ring number 8 9 10 Probability W H Probability W H (a) (10') If A and B each shoots two times independently, find the probability that there are exactly three shots in the ring number of 10. (b) (10') If A and B each shoots once independently, record the sum of the ring numbers as X. find the distribution and expectations of X