[填空题]
A biased coin is tossed 10 times. Let X be the numbe j7w smt 5fs/o+cn*,vbr of tails a:nzjdx49*tx obtained.
The probability of obtaining a tail in any one throw is p>0 .
1. Find, in terms of p , an expression for $\mathrm{P}(X=8)$ .
2. a. Determine the value of p for which $\mathrm{P}(X=8)$ is a maximum.
b. For this value of p , determine the expected number of tails.
