28. a)How many 4-digit numbers can be formed from the set A = {0,1,2,3,4,5,6} if there is no repititon?

***Don't need help solving this... But it has to do with the other questions I need help with ***

c) How many of the numbers in part a) contain a 3?

* I know that numbers such as 0321 can't count because that actually represents the number 321. This is my thinking process thus far.

First digit (6 choices - excluding 0)

2nd digit (6 choices - can't be the 1st digit choice)

3rd digit (5 choices - can't be the 1st of the 2nd digit choice)

4th digit - I know I have to incorporate where the 3 is? I was thinking about adding it to the total?

If someone could show me how to solve thiscorrectlythat would be AWESOME!

Also need help with this... d) How many of the numbers in part a) are divisible by 5?

-The examples I have in my textbook refer to dividing many numbers at a time, (Using the Exclusion/Inclusion Principle) - which is why I am confused on what to do when there is just one number to divide.