To find out how many calls Mike processed using Excel, which feature should Amy use?

To determine how many calls Mike processed, the COUNTIF function in Excel is suitable because it is specifically designed to count the number of cells that meet a certain criterion or condition. In this case, if Amy needs to count the entries associated with Mike, she would apply COUNTIF to a range of data that includes the names or identifiers for each call, specifying the condition as "Mike." This will yield a total count of all calls attributed to him.

The COUNTIF function streamlines the task by allowing the user to focus solely on counting instances that match the specified criteria rather than summing numeric values or performing more complex data analysis. In contrast, other functions like SUMIF are used for summing values that meet certain conditions, SORT is for organizing data, and PIVOT TABLE is suited for summarizing and analyzing data rather than counting occurrences. Thus, for the objective of counting calls specifically tied to Mike, COUNTIF is the most effective and appropriate choice.