Permutation and Combination - General Questions

In how many different ways can the letters of the word 'OPTICAL' be arranged?

In how many different ways can the letters of the word 'STREAM' be arranged?

In how many different ways can the letters of the word 'LEADER' be arranged?

From 9 men and 7 women, a committee of 4 is to be formed with exactly 2 men and 2 women. In how many ways can it be done?

In how many different ways can the letters of the word 'BANANA' be arranged?