Please explain all answers

1.The Ecology Club is electing officers for the new school year. The club will elect a president, vice-president, secretary and treasurer. There are 24 members of the club, and all members are eligible to hold any office. No member can hold more than one office. In how many ways can the club select its new officers?

A. State whether the problem involves a permutation or a combination.

B. Evaluate the answer.

2.A computer company is considering 15sites for 3 new retail stores. In how many ways can the company select the new sites, assuming that all of the sites are equally likely to be selected?

3.How many permutations can be formed from all of the letters of the word HOUSTON?

4.A fair coin is flipped 10 times and the sequence of heads and tails is noted. In how many outcomes are there in least 2 tails?

5. A coin is tossed 24 times. In how many outcomes do at least 4 tails occur?

6. If 7 cards are chosen from a well-shuffled deck of 52 playing cards. In how many selections do 2 diamonds occur?

7. Three boys and six girls are being seated in a row of nine chairs on a stage which are numbered from left to right. How many seating arrangements are there if: Girls sit in the first two seats as well as the last seat?