Explanation
SUMPRODUCT Excel function returns the sum of the products of two or more arrays.
Example:
Array a: (a1, a2, a3)
Array b: (b1, b2, b3)
SUMPRODUCT(Array a, Array b) calculates the following:
a1*b1 + a2*b2 + a3*b3
Syntax
=SUMPRODUCT(array1, [array2], [array3], …)
Each array can be represented by a column or a row.