reinstall app store application

I've deleted (foolishly) the app store as it wasn't working properly - it's was completely removed, not just removed from the dock. Now i'm having alot of difficulty reinstalling the app store application. I need help please!

After some googling, the suggested method was to download the 10.6.6 combo update package and use pacifist to install the app store component. However this didn't work, the app store won't open after this process. I then tried installing app store component using pacifist from the 10.10.2 combo update to bring the app store up to date, but still it won't open.

Does anyone have any suggestions? I've got problem report if that would help.

Alex

Product details:

Macbook Pro mid-2012

iOS Yosemite 10.10.2

Processor 2.5 GHz Intel Core i5

Memory 4 GB 1600 MHz DDR3