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: employment activity 
Words: promote, ice, retire, ban, fire
ice

Category: type of sandwich 
Words: submarine, group, club, roll, grilled cheese
group

Category: police punishment 
Words: decent, penalty, money, ticket, fine

decent