Can anyone Suggest me a good configuration at Rs. 12K

I m very new to this so m asking
I need a PC for my Little Cousin Bro & Sis
They are in 7 & 8th STD
I need to make a PC for them which is around 10-12k bcoz i cannot spend more than that,
They Need just for Playing Games, Music, Internet Search, Fun & just for making a little School Projects in Word, Powerpoint
I have never assembled any PC so i dont have any idea about this
Need Name & Rate of
1. MotherBoard - ?
2. Processor - ?
3. RAM - ?
4. Samsung HDD 40GB is ok
5. Samsung OR Philips - 15" or 17" Monitor - ?
7. Samsung CD Rom/Writer is ok
8. Cabinet & SMPS - ?
9. Any Normal Speaker is ok
10. Any Keyboard, Mouse is ok

Pls help me Friends