Category: Lookup and reference
Uses an index to choose a value from a reference or array
INDEX(array, row_num, [column_num])
Category: Math and trigonometry
Returns the sum of the products of corresponding array components
SUMPRODUCT(array1, [array2], [array3], ...)
0
The SUMPRODUCT function checks for the non blank cells and sum ups the total count. The count is feed to INDEX that bring back the respective data from the array.