Whether you use a calculator, spreadsheet, or other program to do these, the most difficult part is the data entry. The formula is trivially simple: multiply each rating by the associated weight and add the results to get the total for each option. This operation is handled automatically by matrix multiplication.
Multiply the weight vector by the factor matrix. The result is the vector of composite scores:
A: 85.08
B: 86.41
C: 91.60 . . . . . maximum composite score