Formula

Question 1

SUMPRODUCT

Answer 1

to sum the result of multiplications:
=SUMPRODUCT(([array1]=condition)[array2][arry3]***),
condition: and *; or +
https://www.youtube.com/watch?v=lzjc_eEISe8
https://www.xelplus.com/excel-sumproduct-formula-easy-explanation/