Count of Occurrences

Hey...

I have a table as shown below:

Note:

Highlighted red is for repeated ID's.

So basically what I want to achieve is:

1. How many New ID for a particular month, let say in March, there are 7 new ID (colored blue without red cell in left)

2. How many ID that repeated for a particular month, let say in March, there are 2 repeated ID (colored blue with red cell in left)

3. How many ID that stop repeated for a particular month, let say in March there is only 7 ID that not occurring anymore (the id that appears in February but nor appearing anymore in March) 

do you guys have any solution for me?

thank you very much