53486 Countdown w/ cookies

here's what I need: when a user enters the page, I need the JS to randomly select a countdown value between 7 and 11 minutes then store the expiry time in a cookie that lasts for 1 week. This way if the user refreshes the page, the countdown will look like it's real, and not random at each page refresh. When countdown reaches 0, I want some specific text and link to replace the countdown. If user comes back to page after countdown expiry, specific text should appear right away. This is an easy project that can get you an easy 10 rating. Completion is expected in less than a day. Thanks.