sum cells in a row if two text cells match in separate columns

I have multipul columns of names in sheet1(I1:I) and also multipul columns of names in sheet2(A1:A), sheet2 also contains 12 months of sales quantities in corresponding columns (R,S,T,U,V,W,X,Y,Z,AA,AB,AC)
Im trying to sum the total value of the twelve monthes if a name in sheet1 is matching a name in sheet2.