What is the difference between these sentences in American English?<br/><br/>1)<br/><br/>a)He is available between the hours of 4:00Am and 2:00Pm.<br/><br/>b)He is available between the hours 4:00Am and 2:00Pm.<br/><br/>2)<br/><br/>a)Have had<br/><br/>b)Had<br/><br/>Thanks <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'/>