1. Library A: 1 With and without books, the probability of having books is1/2; 2. If books are borrowed but not returned, and the borrowing probability is 1/2, then the borrowing probability of library A is1/2 *1/2 =1/4. Similarly, the borrowing probability of library B is 3/4* 1/4.

Second, the probability of students borrowing books is:1/4+3/4 *1/4+9/16 *1/4 = 37/64.

Note:1-1/4-3/4 *1/4 = 9/16.