Given a category and a set of five words, find the word from the set that does not belong (i.e. is the least relevant) with the other words in the category. Words are separated by commas.

Category: secretary duty 
Words: file, organize, schedule appointments, answer calls, program
program

Category: bird 
Words: ostrich, digger, sandpiper, crane, goose
digger

Category: secretary duty 
Words: prepare, schedule, sort mail, format, file

format