Hi Karanika
What is the price of material in plant B? you can find the same in the accounting 1 view.
In case plant B has some other price, eg 6, the new materials in plant B will be with price 6,
Incase, you have moved the materials, al you have to do is modify the price in plant B using tcode MR21
This will let you have the new price of the material to 8
Regards
Vivek Singh