__The question is:__
John needs to choose randomly 20 chocolate coins from a jar containing 65 coins.

30 of the coins in the jar are green, 15 are yellow and 20 are red.

The parts I can't understand are:

__Case 2 is:__ If all the coins from the same color are identical, how many different chioces are there ?

**Part B:** What is the probability that between the 20 coins that john will choose there will be 11 green coins and 4 yellow coins excatly?

**My try:**
About Case 2- It's the number of soloutions to the equation:

when 0<=x1<=30,

0<=x2<=15, 0<= x3<= 20... But how can I calculate this number?

About part B: I think the solution is

but I'm not so sure...I'll be delighted to get some verification on this ....

Thanks in advance