Calculating Sum of Column by Column

Hi, I have no idea about excel formulas or programming whatsoever and I need your help guys.
I am making an order for my shop and I want to multiply product price X (Column #1) with quantity Y (Column #2) and sum it. I have a picture attached to help you understand better what I want.
uznSuuc.png
I want it to be A2*B2+A3*B3+A4*B4+A5*B5+A6*B6+A7*B7=Z (Total)

Thanks in advance guys!

BTW My office version is 2010.