XCode 6

I bought a second hand Macbook 2009 which was already upgrade to Yosemite but i am not able to install XCode 6 on it using App Store. I do see Install button but it is disabled.

Machine Config : 2.13 Ghz Core 2 Duo with 4 GB RAM on it.

Color: White

Model: Macbook White 2009

Any suggestions over it ? Is XCode 6 not meant for old Macbooks ?