permutation and combination

1. There are 11 books on a shelfin a library. 3 of them are the same and 2 others are also the same. How many ways of arranging the booksare there if the same books
are placed together?

2. 3 students are chosen from 8 stidents of different height.
a. how many combinations of students are possible if the tallest and the shorteststudents are chosen?

b. using result of (a) , find the number of combinations in which the tallest and the shortest are not chosen at the same time.

c. using another method, find the result of (b)


Thanks a lot!!!!