How to use minus formula in sumproduct

Hello All,

I want to minus negative score from total score. Example:

Let's take one positive survey will give 100% score and one negative survey gives 0% score. If we get 10 surveys out of which 9 are positive and 1 is negative, so the score will be 90%.

A11=100%, A12=0%
B11=9, B12=1

The formula is =sumproduct(A11:A12*B11:B12)/sum(B11:B12)

Now I want to remove that one negative survey from the total score of 90% using sumproduct formula. Please help!!

Attached is the file for better understanding.

Thanks.