Hello, should I use 'for' or 'of' in the question below? I know that the question does not make sense but can we pretend that it does <img class='emoticon' style='Width:19px;Height:19px;' data-delaysrc='https://uat-englishforward-forums-backend.s3.us-west-2.amazonaws.com/Emoticons/1.gif' src='https://uat-englishforward-forums-backend.s3.us-west-2.amazonaws.com/Emoticons/1.gif' alt='Emotion: smile'/><br/><br/>What are the rules of the letter A?<br/><br/>Or<br/><br/>What are the rules for the letter A?