Sample table below

The formula will be in cell f5

=IF(f1:f4)="N/A","N/A",SUMPRODUCT(f1:f4,$A1:A4))

If cells f1 through f4 equals "N/A" (which is text I put in there) then in
cell f5 show N/A, but if f1 through f4 equal all numbers then equal f1:f4
mulitiplied by a1:a4.

I will be using this formula in b5, c5,d5, e5. The actual table is bigger
and the numbers will change.

A B C D E F

1 10% 15.58 38.50 26.68 9.43 N/A

2 10% 13.51 36.03 24.85 6.41 3.34

3 4% 8.41 28.66 20.26 4.86 N/A

4 4% 3.67 1. 36 15.75 9.89 9.2

5